In your Instant Pot's inner pot, combine chicken, caesar salad dressing, and water.  

Secure the Instant Pot lid and rotate the pressure release valve to "sealing."

Cook on high pressure for 15 minutes, then quickly release the pressure and remove the lid.  

Shred the chicken.  You can shred it using an electric hand mixer, kitchen shears, or two forks.  You may want to shred the chicken on a cutting board or in a bowl.  

Place the chicken back into the inner pot. You may want to discard or drain extra liquid still in your pot.

Mix in parmesan cheese while the chicken is still piping hot.