Yes your arrival flight number is important helpful information for the car rental company if you are collecting a vehicle from an airport. Your flight number will indicate to the rental car company which terminal you will be arriving at (Domestic or International Terminal).
Once you arrive at the airport and after you have collected your luggage from the baggage carousel, look for the signs which will direct you to the rental car counters. All of the rental car counters will be located in the Arrivals Terminal, so you only have a short walk to their desk.
If you experience a flight delay and the rental company is aware of your flight details, they are more likely to hold the vehicle for you. Without arrival flight details in your reservation and if you haven’t collected the vehicle at the booked time, they may treat your reservation as a ‘no-show’ and release the vehicle to another customer.
The staff at the rental car counter will talk you through the details of your reservation and go through the insurance liability options available and any other options you wish to add on. The counter staff will also talk you through where to collect your rental car, where to return it, what to do with the keys at drop-off. You can ask them where the nearest petrol station is so you can make sure it is fully refuelled when you return the car, what type of fuel the vehicle takes and ask about toll charges.