Changing the shower outlet from bottom to top?

I have recently bought a Bristan Java shower valve and it says that I can have the outlet from the top or bottom, but the top is plugged with a round cap that I cannot get off. I don't want to get the grips on it if it is going to tear the chrome to death and achieve nothing. Any ideas please. It's getting to the point where the Mrs is just telling me to go and buy another.