You first want to take the corned beef brisket and add it into the Instant Pot.
Toss in your water, spice package, and garlic into the Instant Pot.
Set the Instant Pot to the "Meat/Stew" option and cook for 90 minutes. You also can choose "Manual" and click high pressure for 90 minutes.
Quick release the pressure once the timer is up.
Remove your corned beef and place onto a platter.
Put the cabbage, carrots, and potatoes in the Instant Pot.
Cook on "Manual" at high pressure for about 5 minutes.
Quick release the pressure and your corned beef and cabbage meal is done!