Turn on Instant Pot saute mode. Melt butter and saute apples for 3 minutes.
Cancel saute mode.
Add the rest of the ingredients
Press porridge mode and set the time for 1 minute. Make sure the vent is in the "sealing" position (see note).
When the Instant Pot beeps, carefully move the vent to the "venting" position. I use a wooden spoon to do this to avoid burns. Let it vent completely before opening.
Notes
The Instant Pot will take a few minutes to pressurize and de-pressurize; you don't need to push anything to make this happen. It will happen automatically.
Sometimes the IP can give a burn notice when cooking oatmeal. I don’t have this problem in my 6 quart but I have had reports of it happening in the 8 quart. The oatmeal will not burn, but it may be golden brown on the bottom. This is normal and fine.
Don't try to freeze this oatmeal as it will become very mushy when thawed.
For an added delicious taste and texture, you can top the oatmeal with nuts (pecans, walnuts, or almonds) or dried fruit (raisins or cranberries) after cooking.