Scan the image, make it something reasonable size wize, no 3000x2000 res please- 640resolution for pictures is plenty, 800 or 1024 for line drawings is usually good and save as JPEG or JPG.

I upload the hard way, type a post, then go back & edit that post and there is the Upload Files under the text area while editing... I know there is a better way, but I'm a stick in the mud