I just posted some things for sale in Parts and Accesories but when I click on New Posts it doesn't show up. I'm relatively new to this so what, if anything, am I missing or doing wrong. Thanks!
It won't show up in new posts for you because you created it. It has already been open in your browser. When someone else posts to it you should once again see it in your new posts feed.
You can also click "Watch Thread" and it will show up in your watched threads list if you want to follow it that way.
If I'm understanding the issue, the answer is that you won't see your own posts as "new". You can look for the thread in the list by clicking on Forums.