Shooter PID loop

[Teamcodeorange]

I know this has been asked many times before, but none of the answers I found are clear enough for me. How exactly do I program a PID loop to make sure our shooter is at the right rpm, compensating for variables such as battery voltage?

I know labview pretty well but PIDs look really complicated. We have a flywheel shooter with a US digital encoder. I would like to be able to input any rpm value I want (eg 1-8000 rpm) and have the motor automatically speed up or slow down to ~+/- 100 rpms of the requested speed.

Any help is greatly appreciated.