Rather selfishly, I'd most likely use it for either personal betterment or to simply experience something amazing. Deciding which one is something too difficult for me to think about for now, but I'll narrow it down to a few options. Off the top of my head: I could spend an hour with Christopher Hitchens, chatting over a few glasses of scotch; meet Bertrand Russell; watch Queen play at Live Aid 1985; witness Alan Turing's computer being built, and obviously the whole lottery thing, although I see that as a wasted opportunity with such an extraordinary power at my disposal as time travel.
If I were to attempt to make the world a better place, I'd have to first consult a historian. I don't know enough about history myself to know where I could make the most beneficial change in an hour. I'd also be a bit scared of how things would change. The butterfly effect is something that would constantly be on my mind, so making any changes that aren't fairly recent would probably be out of the question. As much as I believe Islam to be akin to a malignant tumor on society which should be cut off, I can't be certain another barbaric war lord wouldn't take Muhammad's place in Islam if I were to stop him from being born, or simply another just as violent religion.
Overall, I'd probably end up overthinking things and use the power to give my younger self advice. Namely to do with the pursuit of knowledge and my interests, as it took me until I was around 16 to discover something that I could be passionate about. I'd also tell my younger self to tell/write letters to anyone I admired, as I regret not doing so while these people were still in my life/alive, as well as all the general advice one would give to their younger self: study harder at school, take advantage of your youth to make as many mistakes and ask as many questions as possible, etc.