yeah, it should be in a manual. if not look hard for 3 pins on your motherboard with a jumper on 2. Look at the fine print next to the pins and it should say "CMOS" if so turn comp off, unplug it from the power cord and move the jumpers from 1+2 to 2+3, let it sit for a few minutes, then move it back to 1+2 and plug and turn on.
If you have looked EVERYWHERE and cant find anything, then just unplug, and pop out the BIOS battery for a few min, and put it back in.