You can add pictures to posts in one of two ways: as an attachment to the post or thread (you can't use the Quick Reply button in order to do this, just use the normal Reply button). Or the way George suggested, by first uploading it to your album. You can create a new album here:

http://forums.psychcentral.com/album.php?do=addalbum

Add your images to the new album, then you can copy and paste the URL from the photo to your post.