How do I make it to where when a player sits on a Vehicle Seat GUI pops up on their screen?

How do I make it to where when a player sits on a Vehicle Seat GUI pops up on their screen? This is as far as I've gotten knowing what I know at the moment.

Workspace = script.Parent.Parent.Parent.Parent


function OnTouched(Player)
    if game.Players:GetPlayerFromCharacter(Workspace) then

    end
end

script.Parent.Touched:connect(OnTouched)

I don't know if this is all correct. Let me know what I should do and if you could, tell me what part(s) in scripting I should learn so next time when I want to do something like this I know exactly what to do. Thanks