Writing a letter toImam Mahdi Al Qaem - ajtfs
Partcularly on 15 Shaban night

A letter is written to Imam Mahdi Al Qaem - ajtfs on the night of 15 Shaban as follows This is then dropped in the sea/river/well etc).
Ariza can be written to Imam-e-Zaman (a.s) whenever you feel a need or you are into a problem. No matter how big is your problem Imam-e-Zamana is the Imam of our time & HE is a Hujjat from Allah (s.w.t). Allah has granted him the power & because of his exsistence this entire universe is in to exsistence
You can write in any Language or your own too.
Our beleif is that Imam (a.s) knows about all our affairs and is always ready to help us. He is aware of our action & he helps us even if we don’t ask or seek His (a.t.f.s) help.
“We are never neglectful of your guardianship nor are we ever unmindful of your remembrance”. (Behaarul Anwar, V. 53, pg. 176) But if we write Ariza to Imam (a.s) then or belief comes to our action. In morning of 15th shabaan ( The time of birth of Imam mehdi (a.j) is the best time to send ARIZA to imam e zaman (a.s)). He read our wishes and also solves our problems.
We can also send this ARIZA on any juma also.
ARIZA Details- Chapter from Sahifa Mahdi

We Should inculcate the habbit to write to Imam (a.s) whenever we are in difficulty rather than approaching someone who doesn’t has the power on any thing. Rather than writing a letter to a Minister or President we should write to our Master who has the control of our all affairs.
It always goes to Allah (swt). But unlike us, Imam (a.s) are infallibles and they hold a MUCH greater position infront of Allah (swt) and if we ask them to put forth our request in front of Allah (swt), if we go through them then Allah (swt) is going to accept our prayers faster. As has being said many times, tawassul is not wajib. You can pray directly too
Your basic intention should be to ask the Imam to interceed on your behalf Inshallah Imam (a.s) will heed your call.
Below is the Answer by Moulana Sayyid Muhammad Rizvi on Ariza.
Ariza is basically a du`a which, instead of saying, you write it down on a piece of paper. There are ahadiths where the Imams have told us that we can write down our prayer (du`a) in a paper and put it in a well or a river. See for example, a similar hadith in the last section of Mafatihu ‘l-Jinan under the section “ruq`a-e hajat”.
How it reaches how is not our concern. The God who can hear our voice, surely has the power to know the du`a we have put in writing. As for the curiosity of your brother; I would strongly advise against opening up the ariza or ruq`a-e hajat. If he believes in it, then he should not touch it; if he does not believe in it, then he does not have to write an ariza–it is not wajib.

Ariza from Jamkaran Mosque | PDF

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Another format

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Translation of Dua-e-Ariza
I have written to you O my master, may His mercy and blessing be on you, seeking a favour from you.
I have complained to you for what has happened to me seeking solutions firstly from Allah and then from you for a matter that has obsessed me.
I am helpless in combating the problem and for that I have resorted to seeking help from Allah and from you. Knowing the status you have with Allah.
I am confident that you will help me get the solutions to my problems swiftly and that you will intercede on my behalf. I am helpless and moreover I am sinful:
so help O master and present this problem to Allah and I pray to Him that He will solve this quickly and grant me victory and success in finding the solution to my problems.
(Write your personal wishes and problems in the provided space)

I am not able to carry or bear with it. Although I am responsible for the increase of my sins and ignorant about my responsibilities (Wajibaats), from Allah which are given to me.
So help me O my master. Peace be upon you during this time of problems and sorrow.
presents my prayers to Allah before I compensate and before my enemies engulfs me. For you have shown me your blessings.
So I pray to Allah for great salvation and near victory with calmness from all fears,
for Allah is most high and does what he wants. Allah is sufficient for me from beginning and in my hopes.
Whatever Allah wish there is neither strength nor any power except in Allah the High, the Great.
*When dropping the Ariza in the sea, we normally recite the following, addressing Husayn bin Rawh, the 3rd Na’ib of the 12th Imam:
“O Husayn bin Rawh, Salamun Alykum.
I bear witness that you died in the path of Allah and (hence), you are alive and are sustained by Allah. am addressing you in your life which you lead with Allah – this is my note and wishes to the master of the Era, the 12th Imam (AS), so please hand it over to him for you are indeed trustworthy”.

Alternate Translation
I have written O my master (A.S) seeking help, and I complain (to you) about what has descended upon me - seeking refuge with Allah (S.W.T) and then with you, from the affair that has taken me by surprise and occupied my heart, and made me think a lot, and has stripped away from me some of my core, and has changed the great blessings of God that is with me, my close friend has left me when it came to me and he dissociated from me when he saw it advancing towards me, my plans have been unable to push it away, and my patience and strength haven't been able to bear it. So I have taken refuge with you in this (problem), and with regard to the request for Allah - I have placed my trust in Allah (S.W.T) and in you, seeking protection from (that which bothers me) - (requesting) about your whereabouts from Allah, the one who brings close, and is the owner of all affairs. I trust you with regards to the speedy intercession (you have) with Him in my affairs and I have certainty in Him answering you with respect to my needs. O my master you are worthy of actualising (what's in) my thoughts, and honouring the hopes I have in you (with regard to) my affairs/matters :
[mention your wants]:

In this (the wants) I have no strength in bearing it and no patience, while you are able to (solve it) although it (the situation) is because of my own ugly acts and my negligence of the obligatory acts which are for Allah (S.W.T), So help me O my master (A.S) in my worries and present my wants in front of Allah, before the starting of the calamities, and the mocking of the enemies (of me), for with you (lies) the spreading of the bounties upon me. And I ask Allah (S.W.T) for an honourable victory for me, and a close success which entails me reaching - my hopes, good principles,completion of my acts, and safety from all forms of fearful things in all states.Surely He(Allah) does what He pleases, and He suffices me - the best of those upon whom trust can be placed in the beginning and at the end.