I scrolled through to see if anyone had answered this specifically, and didn't see one, so if this is a repeat of info, just ignore it
There are booths located on the Boardwalk, near Space Mtn, by Primeval Whirl, and by the Imagination Pavilion...there's probably one at DHS but we haven't noticed it!
You go in and take the picture as usual, picking your border/theme/etc, and instead of buying the print, you use the touch screen to pick the "download to Memory Maker" option. You not only get the photostrip digitally added to your MM, you get each individual photo from the strip added.
You do not have to buy the printed photo to get the pictures added to your account, just fyi!
All instructions are pretty easy to follow (on a touch screen).
I hope that helps! We love the photobooths and won't be passing them up ever again