Hi there
Recently used this service - Antalya airport to Antalya Otogar. Coming out the front of airport, turn right, you will see a bus stop by the taxi rank. Look for the red and black bus, number 600. This will take you to the Otogar. Paid 2tlr each. Leave enough time e.g. 1 hour, goes aroung the city first.
Hope this helps.