Attach the 5v from the USB (or a 5v powersupply) to the pin labeled VCC on the ATTINYs datasheet.
VCC is Pin 8 on the ATTINY
http://forum.allaboutcircuits.com/attachment.php?attachmentid=25565&stc=1&thumb=1&d=1292549744
VCC is Pin 8 on the ATTINY
http://forum.allaboutcircuits.com/attachment.php?attachmentid=25565&stc=1&thumb=1&d=1292549744