At the top, where it says "Community" is a drop down menu. If you go to Forums you will find the discussions. There you can press the Add button at the top to add your own discussion. Or, you can go to one of the catagories and post comments on other discussions.
You can also visit other people's pages. You can do this at any time by pressing their name or pic. You can comment on other pages just like I can comment on yours.
There is alot more that you can do but that's the most important stuff. Have Fun!