Put it in a bowl, add water or milk, turn on the microwave 1 minute and wait. If it's not hot, do it again for another minute.
I have found with oatmeal, if it's in the microwave too long it will boil over, making a mess. So the 1 minute intervals work very well.
It works with minute oat meal or the old fashioned cook-em on the stove Quaker Oats.
Instant packages work great. Use them at work all the time. Put 2 packets in a Styrofoam coffee cup, add a little hot water from the coffee machine and done!
If no hot water, plop in the microwave for 60 seconds! done! Hot. Good!
Add a few chocolate chips (or Hershey's Kiss's), and marshmallows, and enjoy!