Plug USB into the back of TV.
A message may pop up saying, "A USB Media drive was detected - Would you like to browse the digital media files on this drive, now?" click confirm if so. Browse to the location of the file in folder "Photos." If no message pops up, you can also find it by using the top Menu bar to navigate Apps and clicking the DigitalMediaPlayer app.
Click on any photo once you have the folder open and press the Menu button on the remote (right above Channel Up). Click "Repeat" then "Repeat All" to set the photos to repeat. You can also change the duration to Long so that the photos don't move too quickly through the slideshow.