When you are posting, there are 'additional options' below where you type, and its in the part that says 'attach files'. You press the button 'manage attachments' and then search for the pic you want to post.
when i had problems posting i had to go in my files and adjust the size of the pics to the best for internet size, and resave them into seperate files.... that was my problem, hopfully it will help
a year or so ago there was a sticky at the top of the photo forum that went into great detail. Maybe I'll write something up and save it so I can cut and paste when questions are raised rather than type the whole thing out every time or hunt the threads for the info I know is there, but can't find.