A car service or taxi is the simplest but if you are willing to go through the exercise, catch the bus from the airport to the Reston Metro station and then the train into Rosslyn station and from there switch to the Orange Line in the direction of New Carrolton. Looks like your hotel is near the McPhearson Square stop on the Orange line. So if you exit at McPhearson, you would walk a block and a half to the hotel.
To get to the metro - this is from the website on transport:
a 10 minute bus ride to Wiehle-Reston East station from Dulles, where you will transfer to Metro Rail. Buses depart every 15-20 minutes to and from the airport. The coach stop is on the arrivals level at door 4.
Unless you have a lot of luggage, this should be easy enough to do on a Saturday. If you look on the hotel website, they estimate a taxi to run about $70 from IAD.
Last edited by profpeabody; Aug 29, 2017 at 9:24 am
Reason: added info