How do I use a ClickDetector properly?

This is what I tried:

function onClicked(player)
	script.Parent.Parent.Parent.Gate.Transparency = 0.9
	script.Parent.Parent.Parent.Gate.CanCollide = false
end
 
script.Parent.ClickDetector.MouseClick:connect(onClicked)

Thanks in advance for your help!

There's nothing wrong with your script in it's current state. Either you're not indexing the 'Gate' properly or you're using a localscript.

Make this a Script if it's a LocalScript

Check your parenting.