See the Driving Directions to the NIH Main Campus.  

Park in the nearby MLP-11 parking lot, which is just outside the NIH campus.    You’ll then need to get a visitor badge from the nearby NIH Visitor Gateway Center. You will be required to show one form of identification (a government-issued photo ID-driver's license, passport, green card, etc.) and to state the purpose of your visit. See the map showing the MLP-11 lot and NIH Visitor Gateway Center (66) in relation to Rockville Pike(Rte 355). 

On exit from the Gateway Center, you will head up a path which leads right to NLM - bear left up the hill, walking past the Natcher Building (45) on your right before crossing the street to NLM.  The meeting is in the Lindberg Room, on the 2nd Floor of the main library, which is the smaller building (38) in front of the taller building (38A). Walk left past the row of parked cars, then bear right, up to the main entrance, which faces Rockville Pike.  Take the stairs or elevator, on the right, up one floor. See the NIH Campus Map.