Classic check-in at the counter is free and opens 2 hours before departure (3 hours for international flights).
Online check-in starts 24 hours before departure, during the process you can choose your seat for free. In the absence of checked-in baggage, you print your boarding pass and go straight to security at the airport.
Alternatively, you can download a mobile app and check in via your phone. You can then just scan the boarding pass from your mobile phone without printing it.