Sterilize instant pot liner by adding 1 cup of water, select steam for 1 minute. (optional - go to step 3 if you wish to skip sterilization)
Remove water and let liner cool before making yogurt.
Add 3 cups of milk to the Instant Pot liner.
Close lid and select yogurt, adjust so that it displays BOIL.
Once done, open and place food thermometer in to take the temperature. Stir around incase it is not evenly heated. If temperature displays 180 degrees F then you can proceed to next step. If milk temperature is less than 180 degrees F then do another boil (repeat steps 4-5 until temperature is reached).
Remove liner from instant pot and place on pot holder to cool. Cool milk to 105-110 degrees F. To cool faster, you can stir milk or you can put the liner into an ice bath.
Take about 2 cup of the milk and mix into your frozen whey.
Once all melted, place whey mixture into the rest of the milk that is in the liner and stir.
Close lid and select yogurt. Default is set for 8 hours.
When done, take the liner out of instant pot and place your yogurt into the fridge (unless you like eating warm yogurt). Check out the end of the video to see how to get whey from your yogurt.