Using the Metro is highly recommended as parking in the area is extremely limited. Get more details at Metro's website.
House Side (south side of Capitol)
Capitol South Metro Stop
Blue Line or Orange Line: Take the Metro Blue Line or the Metro Orange Line to the Capitol South station. The Capitol South Metro elevator is on the Northwest corner of 1st Street SE and D Street SE. Senate Side (north side of Capitol)
Senate Side (north side of Capitol)
Union Station Metro Stop
Red Line: Take the Metro Red Line to the Union Station stop. The Union Station Metro elevator is between the Amtrak station and mezzanine on 1st Street NW at the Amtrak Station entrance.
Map of Capitol Hill