To start a NEW THREAD..... enter the Forum you wish to post to and look near the top and bottom left of the page where you will see the NEW THREAD button, click, type and submit

To post a reply to an existing thread in a forum, enter the thread and you will see the NEW REPLY button in the same areas (top and bottom left) Depending on the theme/skin you are using, it may say POST REPLY etc but they are always in that same location.

To reply to an existing thread by quoting the post you wish to reply to...use the QUOTE button at the bottom right of the post you are responding to.