Regardless of the time of day you decide to fly, the ticket price will remain around the same. Book flights from Tulsa to Latrobe, Pennsylvania as you normally would.
These are just IATA (International Air Transport Association) codes. They are used in aviation to identify and differentiate airports. That’s why a Tulsa Airport to Latrobe Westmoreland County Airport flight would often be abbreviated as a TUL to LBE flight.