Enter the station through the faregates with the green and white arrows lit.

SmarTrip® targets are located on the top of regular faregates and the inside of wide faregates. They are marked with the SmarTrip® logo.
Touch your card to the SmarTrip® target.
When you exit the station, swipe the card again. The display will show the fare charged and remaining balance on the card.
You can also use the SmarTrip® card at Metro-operated parking gates by tapping the card on the exit target. For help or other questions concerning the SmarTrip® card, contact the SmarTrip® helpline at 1-888-762-7874.
Insert your card (face up with the arrow pointed toward the gate) into the slot on the front panel of the faregate.

The card will come out of the slot on top of the faregate. If you are entering through a wide faregate, the card comes back from the same slot into which it was inserted.

When you arrive at your destination, use your card the same way you did to enter the station. Your fare is automatically deducted when you exit and your card is returned if any value remains.
If your card does not have enough fare to exit, you'll need to add money at the Exitfare machine. When you insert your card into the Exitfare machine, it will automatically tell you how much money to add to the card.