If you have HDMI on your PC/laptop, that's all you need - plug the cable into receiver, set up the PC/laptop to use HDMI as sound device, and you're done.
Otherwise - 3.5mm-to-RCA cable will carry on the audio from PC' headphone/speaker output to the receiver. If you have only HDMI avablable on the receiver, you will need a converter from your laptop' video output to HDMI (if it is a PC, a video card will be cheaper and better).