How to make a map chooser?

I highly recommend you use ServerStorage for something like this, not Lighting.

First you need to decide a random map and then teleport all players to a specific part in your map. This code is very simple since I think you're a beginner.

--Map
maps = game.ServerStorage.Maps:GetChildren()
map = maps[math.random(1, #maps)]
map:Clone().Parent = game.Workspace

--Only use this code if you want to teleport all players to one spawn.
for _,player in pairs(game.Players:GetPlayers()) do
    if player.Character then
        player.Character:MoveTo(game.Workspace.MapName.MapSpawn.Position)
    end
end

--Only use this code if you want to teleport all players to more than one spawn.
for _,player in pairs(game.Players:GetPlayers()) do
    if player.Character then
        spawns = map.Spawns:GetChildren()
        player.Character:MoveTo(spawns[math.random(1, #spawns)].Position)
    end
end

--Only use this code if you want to teleport all players but one to a different spawn.
players = game.Players.GetPlayers()
different = players[math.random(1, #players)]
if different.Character then
    different.MoveTo(map.RedSpawn.Position)
end

for _,player in pairs(game.Players:GetPlayers()) do
    if player.Character and player.Name ~= different.Name then
        player.Character:MoveTo(map.BlueSpawn.Position)
    end
end