If I had a time machine I would go back and give myself some lottery numbers(say 10 million$$). And see what really happened at Roswell, in Dallas on Nov. 22nd 1963, the Tunguska Even, see Julius Ceaser assinated, watch Apollo 11, stop events on Dec. 8th 1980 in NY, see the Trojan Horse, Pompeii, Battle of Thermopylae, among many others.
I also want to meet many historical figures/ landmarks, Ben Franklin, Einstein, Hitler(to remind him that he is part jewish), Jesus, Cleopatra, Twain, Abraham Lincoln, Leonardo Da Vinci, the pyramids(Egyptian and Aztec), Seven Wonders, the Roman Coliseum, and many more.
I would also go into the future several times to see what becomes of humanity, technology, and to see what history has to say about my lifetime and how that changes throughout time. I would also attend my own funeral.