Place the rack in the bottom of the Instant Pot and pour 1 cup of water in the bottom.
Optional: Wrap each potato in a small piece of foil and place on top of rack (stacking them is fine — I get about 7 flat on the rack), or skip the foil and just place them on the rack.
Place the lid on the Instant Pot and switch the valve to sealing.
Press Manual or Pressure Cook, leave the Instant Pot at high pressure (the default), and set the time at 20-23 minutes for medium potatoes (see post above for additional cook times). The Instant Pot will begin heating and building pressure, and this will take about 10 minutes. It will then begin counting down.
When the timer beeps, press Cancel and either allow the Instant Pot 10 minutes to naturally release pressure before opening the valve to venting and removing the lid. Be careful because the potatoes are very hot!