The basic idea of the game is the same as Simon Says: you're going to call out something for people to do (that is, an emote!), and the people who do it fastest advance in the game. Specifically, you usually will do five rounds, and whoever is first in each round advances (bring them up to where you are), and then after you have five finalists, you do a play-off (it can either be a single round, whoever is first amongst the finalists wins, or an elimination, where whoever is last is eliminated until there's only one, depending on how long you want it to last).
This is usually run by Periplum in a nefarious-looking costume, where she hams it up a bit as a lieutenant of the big new boss in town, Sharkey, who's looking for new recruits. There's a lot of drill-sergeant bluff here, where she's telling us how worthless we are, and how the finalists are maybe just barely worth being maggot-meat. However, if you want to run the game, you should feel free to make it your own. Put a different 'skin' on the game, use the same rules but a totally different pretext and tone.
One thing that's commonly part of Simon Says that we don't usually include, but which might be possible, is to require that people do the emote only if first told that Sharkey Says to do it. In this version, you're calling out lots of emotes for people to do, and eliminating anyone who doesn't do the one you call; but you're also going to try to trick them into doing one you call out without saying Sharkey Says first, and that also eliminates them. But it's probably too hard to keep up with typing the commands, tricking them, and also calling people out.