I'm not being ignorant here; but if you only ask that, and leave that; there's no point. That's like asking how to make an engine faster. You might not know how to describe it, but just telling us an engine doesn't help.
I'll do what I can though. It in most cases needs to be done in the BIOS. Some motherboards are different but usually can be done by pressing Delete during boot. But aside from that; why don't you give us more information so we can better assist you?