There is a link in the admin nav bar for 'add new rss'
you need to put in the information there, things like which forum the feed will appear in and what username to give to the poster and the url of the feed all that kind of lark. You can setup multiple feeds so then you can have a feed setup under each persons username.
I haven't used this exact one but i did use Inferno RSS (i think that is the name) and it worked fairly well but the built in vb one looks better because it can handle bbcode and html.