how do i make a certain Player a different starter character?

I'm trying to have it to where me, my friends, and supporters will have different types of characters. I want it to be a model that i already made, but it isn't really the starter character roblox gives you. I don't know if i have to do it by script or if it needs a certain name. I'm new to coding and making a game, and that sparked my attention, even though no one really made anything for it.