How to make a script that kicks all players that enter the game except certain people can enter it?

Use the Kick method.

local PlayersWhichCanPlay = {masterhalo55 = true, 
jobro13 = true}

game.Players.PlayerAdded:connect(function(Player)
if not PlayersWhichCanPlay[Player.Name] then
    wait(3)
    Player:Kick()
end
end)

That won't work. (Correct me with proof if I'm wrong)

local people={"trogyssy", "masterhalo55"}
Game.Players.PlayerAdded:connect(function(p) 
local kick=true
for i=1, #people do
if p.Name==people[i] then kick=false end
if kick=true then p:Kick()
end
end)