Can you please be more specific.
Is your database encoding set to utf_unicode_ci?
This should allow you to have Arabic text.

I don't know how to set my database encoding to utf_unicode_ci. I am sorry i am not very good at this, can you help me?

Do you have phpMyAdmin? or can you run 'mysql' command?

I don't know what is phpMyAdmin and 'mysql' command where can I find them?

Kindly ask the admin who installed your site to do that.
Good luck!

Sorry, I know I bother you, but I installed the site and did everything on it and when I began to write in arabic only ??? appeared. I want you, please to give me the first steps which will permit to me to publish things in Arabic and I will continue.

Thank You Very Much.

I found SQL Buddy Database Management I succeed in changing the language to greek but not to arabic

I found only utf8 but not utf_unicode_ci

I'm sorry, didn't mean to be rude. But you really need to know at least the mysql command to know to how to do basic things.
Anyway, tell me, where are doing the installation? is it local or hosted online?
Since you have sql buddy, I guess you might be doing the installation locally.
So, if you open a terminal (command line) and type mysql then press enter are do you see something like mysql> prompt?
I guess the problem now is SQL buddy is setting the collation (locale) to utf_general_ci which is not usable (AFAIK) for Arabic.

Not sure if this'll solve the issue, but it helped solve mine:
<p dir="RTL">this text will display right to left</p>
<p dir="LTR">this text will display left to right</p>