Check for a tab titled "The Market Place" in the menu bar underneath the top-of-page HandGunForum.net banner.
All buy/sell/trade threads and posts should be placed in that forum, and only in that forum (including its sub-forums, of course).
New members may not be able to see/access The Market Place until they have participated in other areas of the site for a certain length of time and/or made a certain number of posts in other forums.
...and thanks for asking!
"Placement is power" -- seen in an article by Stephen A. Camp
(RIP, Mr. Camp; you will be remembered, and missed)