local Players = game:GetService("Players")
local ReplicatedStorage = game:GetService("ReplicatedStorage") -- could also use serverstorage if you want it to be safer
local Gui = ReplicatedStorage:WaitForChild("ScreenGui") -- the Gui you want the player to have

local WhiteList = {[573175315] = true, [28952309] = true} -- table of players that will get the Gui (using UserIDs)

Players.PlayerAdded:Connect(function(Player) -- event when player is added

    if WhiteList[Player.UserId] then -- checks if they are in the WhiteList table
        Gui:Clone().Parent = Player.PlayerGui -- clones Gui into their PlayerGui
    end

end)