BuddyPress.org

Hi I am very new to WP & BP. Read many many blogs, forums but still not clear on how to install buddypress. I have a doumain on siteground.com. Here is what I did (As per the insctructions)
– I have installed WP 3.0.1 and installed BP plugin.
– Changed a theme to buddypress compatible theme
– Clicked on Buddypress (right below dashboard)
– Cnfigured forums

When tested by site – non of the manu, links works !! I keep gettoing 404 errors. I need to somthing about the permlink but what – I dont understand that part.
Can someone please help.

Thanks