As you enter the Arboretum, tell the gatehouse you are headed to the Snyder Building and they can assist you with additional directions
After you gain entry past the Arboretum gatehouse, follow the drive to the RIGHT
Turn right at the first stop sign
Park in one of the Visitor's Center Parking Lot bays.
As you exit the parking lot, the Snyder Building is the building to your LEFT (just east of the larger Visitor Center). You will note a flagpole in front of the building.