Did you put batteries in the keyboard?
Does the keyboard have a little button you push so it can sync to the wireless do-dad?
Did you plug the little do-dad into the usb port that transmits/receives data to/from the keyboard?
Do you have usb perpherials enabled in the bios on your computer?
I just bought a Logichteck K750 last month and didn't have to do anything but plug the little do-dad in to the usb port.
http://www.logitech.com/en-us/keyboards/keyboard/devices/7454P.S. was informed the do-dad is actually called the Unifying receiver. lol