It depends on the forum software you use, if you even plan on purchasing a forum software.
You can use vBulletin (This site runs it), Invision Power Board, phpBB, MyBB, YaBB, etc.
You will also need a webhost, free hosts are not the best, but there are a few like xen web hosting that are not ad supported.

You might need to know HTML if you want a homepage customly or you can just have your homepage as your forum.

It's really easy once you understand how to make the websites

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The "Computer Geek"
/me is a php/mysql developer.
I am learning C/C++ :)