To post pictures ... click on "Go Advanced" in the middle blue box below the Quick Reply message box.
Type your message in the big box at the top of the next screen.
Scroll down to "Additional Options" ... click on "Manage Attachments."
In the window that opens, under Upload Files from your Computer ... click on "Choose File."
You then go to a file formatted as .jpeg or .jpg (picture files) or .PDF (page/s written in a word processing program or desktop publishing program which might also include pictures). Click on it. Then click on ... "Upload."
Its name will show up in that window. Then click in the blue box at the upper right hand corner ... "Close this window."
It is best to keep the memory size small for the .jpeg or .PDF files (under 999 KB, my guess) or it takes too long for them to load. There should be a way when you re-save your picture to decrease the memory size. It shouldn't change the sharpness of the photo.
You can also choose more than one picture at a time.