You have to say a special chant w/ some sort of goofy hat on your head.
Actually, you probably can't w/ an eMachines. If you could, there would be a setting under 'Advanced Chipset' or something of that nature that would allow you to change the FSB. Upping the FSB would cause it to run hotter, that's why you have to up the voltage sometimes as well.
OC'ing is an artform nowadays, there's a couple dudes around this forum that wrote a book about OC'ing, maybe they'll enlighten you as well.