Simple, what would you do if you were omnipotent, able to do literally anything and everything you want? No limits, just unlimited magical power.
I would probably just go around recreating the "pleasure" scene from Bruce Almighty. I'd be an orgasmic God! This is what I mean:
Most Helpful Girl
First of all create a disease that would rid the planet of a good 75% of the human population, then put a brainier species there to keep those humans in control and teach them how to treat this planet properly.
But then there's still hundreds of other planets I need to manage so besides that I wouldn't bother with earth too much.1
Most Helpful Guy
I would just end war and poverty straight away and just make everyone partying billionaires and abolish the law of physics which causes pollution and climate change so the weather is awesome and the air is fresh all the time.
I would also delete things like cancer, disease and natural disasters from existence.
I would make it so nobody aged past 25 their whole lives and nobody died and as the world's population increased then so did the mass and resources of the world.
I would give everyone the ability to teleport wherever they like.1