The Friends of Nunhead Cemetery are based in a portacabin, just inside the Linden Grove gates. Follow the path round to the right. Before visiting please check opening times.
There is no actual postal address for the Cemetery, but these details might help you find it.
If your sat nav requires a number then try “105”. Alternatively you can give it the coordinates “51.464356,-0.053221”.
Buses P12, 78, 343 and 484 all have stops nearby. The nearest British Rail Station is Nunhead, but Peckham Rye is served by more trains.