You can check in online here from 48 hours up until 3 hours before your flight departs. Please see the instructions below:
If you are flying with baggage, check-in your bags at the flybmi check-in desk at least 30 minutes before your scheduled departure time. If your flight is from Frankfurt or Munich, drop your bags at the Lufthansa counter (check the airport monitors for bag drop location). In some cases, you will not be able to check-in online and will need to go to the airport to check-in.
NOTE: It is your responsibility as a passenger to be at the boarding gate in time to board your flight. Depending on the airport, boarding gates can close up to 30 minutes before departure, and you must allow enough time get through airport security and passport control to be at the gate on time.