To attach a file, start a new post (notice, this cannot be done in the quick reply box at the bottoms of the thread, you must either hit "New Thread" or "Reply" to enter the right page. Type out your post, and when you're done, scroll down. There will be a section to attach files, click attach. A new windown will open, and you can browse for where your files are on your computer, when you've found all your files, click upload. Now you can go back to your post, and click submit.

done. easy huh? the only limit is these photos are limited in size, and do not show up in line with your be a real pro, link your files instead (it saves us bandwidth too!).