You need SideQuest, there’s links to a tutorial on how to install this in the description of the video. You also need to connect your headset to PC to transfer the emulator and roms from your computer to your headset. Then, run the emulator, give it permission to access your files. Once you’ve done that, restart your Quest, connect it to your PC and you should see a folder called ‘NES Space’. Copy your roms into that folder. When you start up the emulator again, go into your games library, hit the refresh button and the games should come up.