Since you are into the hobby now, I recommend to begin using eyesight for alignment in general. After a while this "Eyeballing", as it's referred to, is actually quite accurate!

Example: Find any item at home that has a "straight-edge". A Yardstick is ok, but not highly true. Again, hold the yardstick up and eyeball down the edges. You will find out what straight is and is not! (A metal straight edge can be found at a local store at a fair price.)
The sheet of thin cardboard that comes packed with a shirt has a decent straight edge.

Looking down onto the top of the entire length of fuselage, place the straight edge over the center of the engine crankshaft, aligning it with the center of the glow plug. Eyeball the straight edge along an imaginary line down the center of the fuselage, and up through the vertical fin. This yields position of the crankshaft TO the centerline of the fuselage for sidethrust.

Or...Tape(or pin) a strong thin piece of string to the center of the top of the vertical fin. Pull taught and extend all the way to the center of the crankshaft. Eyeball for results.

Of course this is primitive, borderline neanderthal, but you can get a good idea of whats going on.