To post a "New Topic", simply go to the appropriate Forum, and flick the Post New Topic switch at the top of the Forum list, or at the bottom - note that you must be Logged In to perform this operation. When the "Post Box" pops out, fill'er up!
If you wish to Reply to an existing thread, you'll find a "Quick Reply Box" at the bottom of every thread - you can also use the Full Reply Form linked there, which is quite the same as the form used making a New Post. If the post you want to make is not directly relevant to the thread, it's preferred that you "Post a New Topic", rather than "hijacking" an unrelated one.
Notice the icons across the top of each individual post in any thread. These are useful tools. The first: 
will take you to the poster's profile (and clicking on the posters username will, too). The next: 
will bring up the member's e-mail address if they've made it known. The two folks: 
will allow you to "PM" (send a Private Message to) the poster if they've allowed that in their profile. If the member has a web page listed, the 
home icon will be present. The 
will only work on your own posts -- it brings up the "Edit Post" box, so you can change that post of your's that you forgot to Preview, or so you can delete it altogether. Note: if you delete a post that is the first in a thread (a "New Topic" you posted), that will delete the whole thread. Only you or a moderator can delete your post or thread. The final icon: 
pops up the Post Reply Form, already primed with the text of the quoted post you clicked them in - you can carry on typing what you wish to add after that quote, or you can pare the quote down to just the relevant point you wish to respond to. Hovering your pointer over each of these post icons will show an 'address' which will contain terms that indicate the function if you forget.
Note that when you hit the "Add Reply," there may be some delay before the "thanks for posting" message shows up. Sometimes the delay can make it seem like nothing has happened. Have patience -- sometimes there might be a dozen other posts happening at the same time, or the general internet connectivity might be slow. If it turns out that you hit the button twice and actually made two posts, open up one of them and delete it!! If you didn't Preview the reply before adding it, and see an error or omission, click the Edit icon and make the changes, rather than making a separate additional post.
is real close by!
