How to make player skins?

Well, normally I don't answer questions like this, but I'll get to that later.

There's no real way to implement "skins," meaning that ROBLOX has not made an official/easy/non-scripting way to have teams have certain clothing items.

So, this site is for scripters who need help. I'm not sure if you're a scripter or not, but we don't accept script requests.

I will, however, help you with the concept of the script. You need to make the script check which players are on a team, and depending on which team they're on, create a new shirt and pants objects or change the ID of the existing ones to which clothes you'd like. Once you've made that script, if there's errors in it, come back and we can help you fix your script.