[Trent Adams]

You can put the forum wherever you want to be honest, but my directions was assuming you knew what bbPress is. It is a completely seperate software package and needs to be installed somewhere In my example it was mydomain.com/forum/ and I installed it from downloading from https://bbpress.org/download/

That is the first step and most people install it so that it uses the same userbase from your WPMU install (which is part of the bbPress installation steps)

Hope that makes it clear.

Trent