I've been working on a fake arm lately, i've already welded it to the [original] arm, unfortunately, all i wanted to do is do a bit of an animation whenever a specific key is pressed? How am i to start?

part = script.Parent
weld = part.Weld

function buttondown()
	-- What statement should i use to animate it using CFrame?	
end
mouse.Button1Down:connect(buttondown)

Thank you!

Anonymous