How to connect keyboard when I'm on set up

i have just received an IMac 20" refurbished for my birthday from macking.com. As I did not get it from Apple I knew something wrong would happen and it has, i have got a Bluetooth key board and a usb mouse. Right now I'm on set up mode since the only thing that will connect is the mouse as it is connected by wire. The keyboard however needs me to go onto blue tooth setting and add it. Obviously I cannot do that as I am on set up mode and does not let me continue until I enter details by typing it in. Can someone help.