There are two ways to do this:
To clear CMOS using the battery method, simply take out the CMOS battery with your computer power unplugged. There is usually some lever you press down to pop out the battery. Reference your motherboard manual on how to do so if you are having trouble. If you don’t have your motherboard manual on hand just google your motherboard model’s manual.
To clear CMOS using the jumper method, short the two pins as seen in image above with a flat head screwdriver or metal object. It’s usually labeled “CLR_CMOS”