Firstly I don't reccomend punching in a fight, unless you have perfect technique, and good bone genetics in your hand, you're likely to hurt yourself.
If you have decided to punch, then basically the best way to explain it is your transferring energy that starts from your feet against the ground, into the other guys face, and all your body and technique are really doing is minimising the leakage through your kinetic chain.
For a jab or a straight, make sure your feet are correctly planted, and then hold your core tight, but everything else supple, slightly pushing off your front foot snap your leading hand starting the move very slightly after you initiate from your feet, and punch through the target.
For a straight cross it's similar, put you start from back foot and need to pivot a bit, and the pivot timing has to work with your hip rotation, so it's a pretty hard move to do, if you're going to throw a straight right, try to remember it is a strong pushing action, rather than a swinging, and that will help you keep feet balanced.
Hooks and uppercuts are hard to teach because you just end up swinging, so don't bother for now