While having a detailed knowledge of the future might make you popular in some quarters, in Europe, it would most likely get you burnt at the stake unless you were able to make your "predictions" in rhyming quatrains.

However, since the originator of this node did not specify 15th Century Europe, I'd probably just beat the Conquistadores to mesoamerica, convince Moctezuma (or whoever was reigning in Tenochtitlan at the time)that I was a powerful deity (a butane torch, a machine gun and one of those nifty solar-powered cassette players they sell at the Discovery Channel Store would most likely work wonders) and order the Aztecs to kill Cortez on sight while Bjork howled about meeting an Army of her in the background.