Definitely take the metro, lets you off a half block from the entrance. Just time it well to not swell with the masses.

Metro stops within a few blocks include Navy-Archives Penn Quarter, Metro Center and Judiciary Square. Parking in DC is never a picnic, but you do have options! There are multiple garages near the Verizon Center if you decide to drive.

I, and most other DMV (D.C., Maryland, Northern Virginia) natives, would recommend ditching your car and taking the metro. It actually makes it a fun way to experience the area not relying on your car to get everywhere