@stoogesfan87 here are some steps to get the job done:

Copy the PNG to a directory accessible to the pi user (like ~/RetroPie/ROMs/coco/media/images/ From ES, highlight the folder that you wish to display the image Hit your "Select" button Select "Edit this game's metadata" Select "Image" Type the path where the image is Restart EmulationStation

For number 6, I can't remember if you can use relative paths or even the tilde (~) so probably best to use the full path. So for step 1 above, the path would be:

/home/pi/RetroPie/ROMs/coco/media/images/<your_image>.png