Installing new Drivers???

I am new to this ATi stuff! There doesn't seem to be a tutorial at the ATi site to tell you how to install new Drivers... I thought you had to uninstall the existing ones first or something but I don't have a clue! Im downloading the 4.1 Cat drivers now. Its all different to NVIDIA!
Can someone tell me how to do it?
Can someone tell me how to do it?