Thanks. So when you say try to get it down to an accuracy of 1km, do you mean that I just predetermine before I take off "I want a 100 by 150 mile orbit"?
Yes. But learn thinking metric first, it makes the learning in orbiter easier. And as even NASA decided to use metric for their moon landings...
The basic idea of orbit insertion is to get into an orbit accurately.
Say, you aim for 250x250 km first. That is the standard LEO today. When you can get there, you can go into many other orbits, by just burning longer.
Next stage: Orbit plane. Try to launch into orbit, by having minimal relative inclination to a space station. when relative inclination according to Align Plane MFD is lower than 0.02° you are great.
Finally practice the maneuvers to control all your Kepler elements in Orbit (Apoapsis, Periapsis, Eccentricity, Semimajor axis, Inclination, LAN, Argument of periapsis, Orbit Period). Ideally you should then be able to get into any orbit you like. ANY.