Follow this guide. Practice makes perfect
For practice, fly alongside a friendly aircraft and about 30 yards away.
Press F10.
Pause.
Press F2. (This will show an external view of your aircraft).
Slide the mouse to rotate the view horizontally of your aircraft.
You will suddenly 'hit' the view of the nearby aircraft and it's interior.
There are variations on this for different views.
I hope this helps.
Best Regards,
MB_Avro