If you have booked an airport transfer to your hotel, you don't have to worry about anything. You will be taken directly to your accommodation.
If you don't have a transfer, you can get from Sarafovo Airport to Sozopol by bus or by taxi. Passengers can take bus number 15, which stops at the ring road at the entrance to the airport. The bus ride from the airport to Sozopol will take just over an hour, costing 4.5 BGN.