Lot C15 is the lot surrounding KTXT just west of the USA, and you can get to it by Knoxville Avenue and the Texas Tech Parkway.
You can get to lots C12 and C14, which are South and West of the Animal Science Building, by going down the Marsha Sharp Freeway.
There is also a free shuttle service from the free parking at Health Sciences Center.
You can also drop-off concert-goers in front of the USA in the right lane of Indiana.
You can see a map of the parking lots from the official Texas Tech website.