How to….

Ok, I’m new to wordpress, and just trying to figure out what plug in, or tenplate I need to run to get my home page to read like the forums here do. As it is I have 1 post, then people reply to it, and it all goes to a seperate page. Users are not able to start new topics. I would like it to have a grid type layout that would show all topics, and have my users/members be able to post new topics, as well as reply to oners posted.