I would turn it into a TARDIS and try to mess up the mechanism so I only have a vague idea where it will take me. Wear my Third Doctor velvets ruffled shirt and silk lined cape and take a teenage girl with me!
Wherever I go I will remember the effects of the Blinovitch Limitation Effect.
I would like to head for the American civil war, 19th Century rural Appalachia, solve the mystery of the princes in the tower and then hop forward in time and see if I can avert the Dalek Invasion of Earth in 2150 or 2164 depending on what date you believe it happened or will happen.
But that Blinovitch Limitation Effect is problematical. See The Day of the Daleks if you do not believe me.
Craig