Move your mouse to face your target. Adjust position until the cross-hairs are pointing at the target then press left mouse button to fire guns.
Use the red circle as an aiming guide for targeting in-flight aircraft.
Remember that both bullets and rockets are subject to gravity so the further away they are, the higher you need to aim to compensate for gravity.
Click on the mouse wheel or press the “2” on your keyboard to fire rockets.
Use the “5” on your keyboard to launch a torpedo.