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Then "Manage Attachments" under additional options
A new window should open up, hit browse find your photo in your pc files and double click it.
Then do this again in the open spaces if you have more photos to upload.
Then once you've chosen the pics you want to upload hit "upload"
Wait for them to upload(should take a min or two) then you'll see it listed under "current attachments" on that same small window.
Then hit "close window" at the bottom of that smaller window and it should bring you back to your normal reply window, then just hit "submit reply"
There are several threads that tell you how to post pictures. The "Search" feature on this board is pretty brainless and helps out in these situations.