Help with the Luna buses to the airport.

Hello, I am a tourist here for the Ye concert and I'm loving my stay so far but I have a small problem. Im not quite sure how to get a Luna bus to the airport when I have to leave. Do I have to buy a ticket online or in-person, where exactly I have to catch it, etc. The nearest terminal to me is the Tirane north and south. Any help will be very appreciated! Thanks in advance!