They just said "Sir Bertram Stevens Drive, near the Warumbul Road turn-off"
so it looks like that right-hand hairpin as you go south, shortly after you go over the causeway (not long into the drive after you leave Princes Hwy).
https://maps.google.com/maps?q=sir+bertram+stevens+drive+and+Warumbul+Road&hl=en&ll=-34.083766,151.069565&spn=0.021219,0.045447&sll=-33.867952,151.210044&sspn=0.042262,0.090895&t=h&hnear=Sir+Bertram+Stevens+Dr+%26+Warumbul+Rd,+Royal+National+Park+New+South+Wales+2232,+Australia&z=15