Losif,
meanwhile there's a component available which will create all necessary icon images automatically:

https://www.opensource-socialnetwork.org/component/view/4445/favicons

Arsalan, in order to get iphones and some androids to allow the favicon as the bookmark image on the homescreen you have to add it as a link in the header of html. Losif is asking how to find the html header to put the above code in place. The favicon.ico replacement only works for browsers themselves (from my own testing).

I have personally tried the favicon generator and cannot get this to work. The only way I could add any favicons was to do it manually.

Losif - PHP is a server side language, so any html that is generated is not a physical file already created. Each html instance is created on a need by need basis. I am not sure what the answer is to your question. But thought it beneficial to give some background information for others looking for the same information or someone who might have the answer.

OSSN already have a favicon simply search favicon.ico and you'll find a exact place where you can add these codes see https://www.opensource-socialnetwork.org/wiki/view/1137/how-to-find-something-a-word-pattern-in-the-source-code

This is a code that I use on other pages, when you add favicon to the image/ favicon works on multiple devices phone, android, apple etc. my question is? Where can i add him to work? can it be in index.php?

What do you mean? you cant just copy paste stuff in Ossn so please share exactly you are trying to do ?