Two ways:
First, you can do so from your Profile -- if you click the "My Profile" link at top, then near top left you will see a link "Show Posts".
Second, from any thread, you will see user names and avatars (you still need to set an avatar for yourself by the way), and under that you will see a link "Posts: ###" -- click that to view any users posts.
Tip: At the very top of the forum page where it says "Greetings [USERNAME] are also some quick links, and one of them will take you to "Show new replies to your posts", which can also be useful.