If you didn't purchase the Automatic Online Check-in service when making your reservation on the Vola.bg website or didn't purchase a ticket type that includes the Automatic Online Check-in service, you will need to perform the check-in yourself on the airline's website and follow all the procedures imposed by them.
It is recommended to print your boarding passes and present them at the airport to avoid additional fees. Airport check-in can be done directly at the airline's counter or at self check-in machines if available.
For some airlines (especially low-cost ones), online check-in is mandatory. Otherwise, airlines charge an additional fee for check-in at the airport.