Use one of the power molex from your PSU (has 4pins). Make sure you have a free IDE connector on one of your cables. Or make sure you have a spare cable. (i don't know if HD''s come with cables)
then connect the IDE cable to your HD. Make sure the red wire connects to PIN1 on your HD (next to the power connector) The yellow wire from the power connector points outwards.
Look at this, you can clearly see the yellow wire on the power molex and the red wire on the right side of the IDE cable: