Wardman Park is in Northwest DC and is easily accessible via the Red Line on the metro system. If you fly into BWI, there are several ways to get into the District. The best way is to take a train (either MARC or Amtrack) and end up at Union Station (also on the red line). That takes about an hour. Or, take a bus and end up on the green line at Greenbelt (this will take longer as you have to account for traffic, and Greenbelt is further outside the city). If you can't be bothered with public transportation, take a cab or book with SuperShuttle. This might also take a while, depending on traffic (definitely at least an hour), and a cab could cost about $80.