If you’re familiar with playing NES Party with friends, it’s the same setup process. After creating a room, you’re asked to load a ROM file and from there, WebRTC streams the video and controls to the other folks you’re playing with. We tried it out with Bomberman and it went off without a hitch.
Of course, given Nintendo’s litigious reputation don’t expect this service to stick around for too long. Maybe it’ll last until the company gives further details of how and when we’ll get to start playing NES classics with our friends on the Switch. We can always hope.