Put out a lot of convincing TV ads and research papers to convince everyone they are insane and need to take drugs to cure themselves.
Eventually when insanity and drugs are considered normal and enough people are drugged, then use the authority given my team as the experts in the field to declare one by one all the most able people in the world insane and have laws passed that allow you to take them for treatment and drug them or give them ECT or psychosurgery based on the opinions of a few of my colleagues.
Then when the most able are destroyed, the rest of society will be helpess and easy to convince of their need for my help with drugs and other treatments. They'll be poor, despondent and helpless, knowing that they can't do anything anyway, because they are mentally ill and hopeless and need my drugs to be normal.
Then I'd rule the world.
Edit:
Oh yeah and I'd throw in a few general scare campaigns just to keep people nice and scared. Tell them Rapture is coming, the world is warming or cooling or changing or something.