Look at the top of the post box there is a series of icons. Third from the right is a picture in a frame. You'll need to have this feature turned on in your user management section.
Click on that and it will open a box allowing you to browse your computer's files. Click on the pic you want to post, and please try to keep it around 600x800 for those of us on dial up. The bigger pics take forever to load for us.
Then just follow the instructions as you go.
Joe