For directions how to get to Yorktown I can hardly improve on the NPS web page.

This Yorktown Visitor's map will give you an overview on public parking areas in Yorktown. Visitors should park in the large parking lot near the Yorktown Battlefield Visitor Center, the smaller lot at the North end of Zweybrucken Road, the lot on Ballard Street near York Hall, or any of the waterfront parking areas as marked with a blue P on the map.