There should be a couple pins on the board with a jumper on it. If you still have the manual you can use that as a reference, but since it probably didn't even come with one, you're going to have to do it the hard way, with your eyes. Once you find it, there will be a veryyy small legend immediately next to it, showing a box around dots or something to that effect, this is how the little plastic piece sits on the pins for each setting. It should be on default, so use that as a reference. Carefully move the plastic piece over to the clear cmos position, then turn it on. turn it off again after a few seconds, move the piece back to default and boot again. I think some boards use batteries too, which you just remove (carefully i would assume) for 30 seconds before re-inserting and booting to clear, but the boards I've done have used the pins.
Also, on a side note, the motherboard talking to you is the queerest thing I've heard tell of. Its kind of amazing actually. Some mobos don't even beep any more and your's freaking talks, good deal lol.