I have scrivener for Windows on my desktop but I want to install it on my laptop also. How do I do this? As I am an eighty year old technophobe please explain in it simply. 
Install the program on the laptop just as you did on your desktop PC. When the program asks you to enter your registration name and serial, enter the exact same information you entered when you installed on the desktop. Voila, Scrivener!
Many thanks for your help. Much appreciated.