To update simple static content on your Samsung screen with a USB drive you will need to use the following instructions.
Turn off the screen, either with the remote or at the wall
Unplug the USB drive
Take the USB drive and update the content using a Windows PC, ensure the content is a jpeg image no larger than 1920x1080 pixels (or 1080x1920 for portrait screens).
Ensure the content is named the same as it was before, usually 1.jpg
Plug the USB drive back into the screen
Turn the screen back on, the content should auto start.