This article explains how to add games to the SNES Classic using a Windows PC. You will need your own SNES games in the read-only memory (ROM) file format.
How to Add More Games to the SNES Classic
Once you have the games you need, the next step is to set up the required software. You can also use Hakchi to add games to the NES Classic Edition by following the same instructions.
Connect your SNES Classic to your PC using a USB cable. Make sure the console is turned off and leave the HDMI cable plugged into your TV if possible so you can monitor your progress.
Get the latest version of Hakchi 2 from Github. Download the ZIP file and extract the contents to your computer.