When you are done with the ride, you can park the bicycle back to the station. The bicycle will automatically lock itself and you will receive a pop-up confirmation that the bike was successfully returned.
You can also finish the ride inside of the virtual station if there are virtual stations. You can find virtual zones in the map view. To end the ride in the virtual station, you have to close the back wheel lock and press "END RENT" in the app. You will receive a pop-up confirmation that the bike was successfully returned.
WARNING! The end does not rent, if you just close the lock!