Well if I had access to fantastical technology like The Culture from the Iain M Banks novels I'd instantly dismantle all heavy weaponry of all military powers on the entire Earth. Tanks, planes, subs, nukes, artillery, all of it. I'd also sabotage any attempts to rebuild the arsenals.

Then I'd hack all the most popular news media in most states on Earth and show the people the atrocities their governments did and that the current way of doing things is not working at all.

Then I'd just see what happens.