HELP! 66 cuda idles fine, but not when in gear

Ah. Duh. Vcan, got it. I’m sure I’m coming pretty ignorant with all this but when I was a kid and tuned my old Chevy motors I was pretty simplistic with it, no vacuum to the distributor, timing light, 6 degrees or what not. Obviously to really dial it in there is a bit more I need to learn.