How do I make a team exclusive to groups?

I'm starting out a group with a friend and would like to know how to set custom teams only a certain group can join. I'm not good at all with roblox> scripting, and not sure if this is actually scripting. For example, one of the american armies I've found had it so when you join a game, and are in the team, it puts you in that team and shows your rank in the group, along with kills and deaths. This may just be leaderboard specific, like I said, I don't know.

Additionally, if it's possible, are there any ways to make it so others can't join the group team, but you can still leave via That may be something not involved with scripting.nds? That may be something not involved with scripting.