I've put the code below in a LocalScript and inside StarterGui to test how CFrame works.
local Player = game.Players.LocalPlayer
local RArm = Player.Character["Right Arm"]
RArm.C1 = CFrame.new(5, 4, 2) * CFrame.fromEulerAnglesXYZ(1,5,2)
When I play the game nothing happens, why?

2 comments
I thing its called "Right Arm".. Do you have an output error?
Oh, I changed it to Right Arm with a space and now it says 'C1 is not a valid member of Part'.