F6 moves you to the bombsite, hitting "U" starts the bomb calibration mode, and hitting and HOLDING "Y" sets the speed and altitude into the bomb site. The longer you hold "Y" the more accurate your calibration. Be sure to hit "U" again to get OUT of the calibration mode and to get back into the bomb site so you can drop your bombs. Changing altitude or speed means you have to go through the calibration mode all over again.