First of all, if I could do anything in the world, I would be over the moon about my situation. After enjoying this feeling little bit, I would remove all of the pollution on Earth to survive here. (Actually, I could just move to another planet, I would rule that consideration out in this article. By the way, this premise is just limited 'on Earth?') And then, I would make a good environment to make all of the creatures which have become endangered or extinct by human coule live on Earth. I think the equilibrium of ecosystem is very important. Also, it is for making my life more interesting and stable. I wouldn't live in the place which possibly hurts me.
However, I wouldn't change the things that might affect on entire world because I couldn't predict the result. Maybe I would reap the result! I would travel all around the world, especially the countries to which I haven't gone because it was dangerous.
Also I would want to have a big house with a huge property to live with my family. I would eliminate poverty in the world. Unfortunately it is very hard that I come up with specific details about the solution. I might need competent assistants.
I have thought about my other desires, but I think it doesn't have a meaning since I thought I had that ability. After I made my country stronger and enrich my family and descendants, I'd rather get rid of this ability.
That's my answer. Did I take too serious on the topic? :-) Actually I prefer having a large sum of money to having this ability.