To check your PM, click on your ID on the home page list of current posts, or on your ID on the "Members" page. At the top left is a link to "User CP", click that, and you can access your PM's there.

As for attaching pictures to a thread post, at the bottom of the thread is a radio button for "New Reply", use that instead of the grey reply box at the very bottom of the thread. When you get to "New Reply" there is a grey message text box to enter your reply. A couple boxes down is the attachment link. Hit the "Browse" button and find your photo on your hard drive (or whereever you store them) and double click the file. It will be attached and uploaded with your post.

If you want to build a gallery, click the link in the upper left (Orange Hiboy roadster) of the home page or a thread page. Once there, you'll see the link to upload photos, just follow the directions.

Enjoy.