Sutherland and Princes Highway to Robertson Showground  - 136km from Harbour Bridge

Take roads twds Sydney Airport, but remain on Princes Highway heading to Sutherland and twds Wollongong.
After descending Mt Ousley, veer right and follow signs to Kiama/Nowra, remaining on Princes Highway.  Albion Park Rail is about 10km Nth of Kiama.  Veer right onto Illawarra Highway just before Albion Park.  Drive 10km West to start of KOM Climb up Macquarie Pass, a further 12km to KOM of Macquarie Pass and a further 5m to the Robertson Showground which is 1.4km up Kangaloon Rd. 
Pick a camp site behind the pavilion on the highest point of the Showground and assemble your trusty tent.

Below are explicit directions from Engadine to Robertson