Ahh, so basically you want a forum!
Well first of all you will need to find a cms for that forum there are a lot of them out there phpbb, vBulletin, IP.Board, XenForo, Simple Machines Forum, MyBB, and there is a lot more but these are prob the most popular among the internet. Not all of these are free either. However just like fusion cms you install it on your host. Then just change the menu's forum link to your new forums. Of course I am not going to get into the details on how to install any of these its pretty self explanatory. Simple google any of those names and you should be on your way.