Washington DC is served by three airports:

1. Ronald Reagan Washington National Airport (RAC)
   Ronald Reagan Airport is a stop on the Washington DC METRO system.
   Travel time to the conference venue is approximately 1hour with a change of trains.
   Taxis and ridesharing services, e.g. UBER, are available
    
2.  Washington Dulles International Airport (IAD)
   IAD is approximately 50 km (30 miles) to conference venue.
   Several transportation options are available, including the METRO. 
   More information for travel options are avaialbe freetoursbyfoot and at tripsavvy.
   Taxis and ridesharing services, e.g. UBER, are available.
    
3.  Baltimore/Washington International Thurgood Marshall Airport (BWI)
   BWI is approximately 65 km (40 miles) to conference venue. Several transportation options, including Train are available.
   More information can be again found at freetoursbyfoot and tripsavv
   Taxis and ridesharing services, e.g. UBER, are available.

Soem other useful links are :

https://www.wmata.com/

https://www.wmata.com/rider-guide/airport-and-rail/index.cfm - gives instructions for trasnfers from Dulles to Washington

Aslo to travel on the Metro you will need to purchase a SmartTrip Card.  SmartTrip cards are available for purchase in every metro station, and there are instructions posted on how to use them and how to charge them at the Metro Stations.