Hi @Charles_L,
We have a great section on this forum called #tutorials where you can check out some tutorials for using ATC and flying with it. I have managed to find two that I think explain it the best.
I also recommend checking out tutorials for ATC, even though you might not use it, it will help you understand the instructions and how they apply to you. If you have any more questions feel free to PM me and I will be glad to assist.