Welcome aboard Princess! Please allow me to be the first..(as I'm sure there will follow more!)...one to welcome you to the forum!
I would assume by tutorial you are referring to the "Academy"...and hence the Flak Gun Exam... The trick here, is to lead the target, well ahead of its flightpath, as it takes some time to get those bullets up there where he is.
Have you installed any of the various "Mods" found here?