Once you have arrived at Dulles International Airport and gone through TSA checkpoints, it is very easy to get around and between terminals. However, there are a few options that you can try to move between terminals and gates.
Passenger can transfer between terminals by Aero Train, and it's an underground airport train system connecting the Arrival Terminal. Also, it moves you to A, B, and C gates. The whole process will take less than 2 minutes. It is available for domestic and international passengers.
Airport Shuttle Bus
There is a free Airport Shuttle Service that connects the Arrival terminal with Garage 1.