Hello !
Sorry to bother you. I found this forum when looking through google for forums to use. I need
to install a forum on my website but I cannot find where it is sold.

Where did you get this one

Thanks for any assistance

You can buy this one at http://vbulletin.com . It's arguably the best forum software on the market.

If you don't want to go with a paid forum there are tons of great free options also. For free I like http://phpbb.com .