Alright, first order of business would be to have a fortress built. Only I would have the passwords to the inner sanctum, as I would have everyone who programmed the passwords executed via grenade taped into their mouths.
Next, I would work on an outwardly good appearance by canning all the breast cancer awarness fundraising and redirect that money into breast cancer cure research fundraising. I would also spend enough time to replace every current politician with 4.0 gpa highschoolers, since they tend to be less greedy and corrupt than someone who is already a politician.
After all politicians are replaced, I would unite the world with severe laws against any sort of hate crime, with punishment being fine, second offense jail time, third offense limb removal. And all murderers will face firing squads.
After a year, I would drop my good act a bit by ordering the execution of the top richest 15% of the worlds population under the guise of treason, send half their wealth to research for curing diseases and planetary colonization, and the other half would be put in several large pits across the world for people to take from if they so pleased (which they likely would)
After a few more years, kill off one fifth of the world's population and pose a child limit of two children per couple with the exception of adoptions. And once a person has had two children with anyone, mandatory vasectomy to prevent further overpopulation. The only time the limit would be lifted is when we start to colonize planets.
When technology has advanced enough, I'd have a team of trusted scientists and doctors turn me into a cyborg with the potential to live forever, and offer the same benefit to my staff as a reward for complete loyalty to me. Once they accept, add a special package of data that ensures they can never turn against me.
Pretty much the theme of me being an evil overlord is be evil to save humanity (not that it deserves it, but it would be pointless to be the evil overlord when everyone's dead.)
Oh yes, and I would also make Wicca an official religion, because I'm not an ignorant fuck-tard like most religious zealots are!
And for the hell of it, any kind of sexuality is legalized.