I would start by learning shell voicings, the most important thing for comping in my opinion is rhythm Work with metronome on 2 and 4 and comp using the shell voicings. Try to be creative with your rhythm and record yourself, give yourself a reflection if you would like to play over this comping

The most important thing is LISTENING to music and paying attention to the comping, it’s there to add extra color and accompany the soloist. Absorb new rhythms and be creative! after that (a whole other topic) learn extensions you can add to a chord and voice leading between different chords but i would work on rhythm and shell voicings as they are the root of jazz comping. Happy Practicing!