Hey.
You can request the players name through the PlayerAdded function and use it like so.
game.Players.PlayerAdded:Connect(function(Player) -- We request the player's name
local teams = game:GetService("Teams")
local player = game:GetService("Players")
local newTeam = Instance.new("Team", teams)
newTeam.Name = Player.DisplayName -- And we get their display name and assign it to the team's name
newTeam.AutoAssignable = false
end)
Hope this helps.