The entrance to the Battlefield is shown where the red star is.  Continue up the hill as indicated by the road from the SE tip of the star.  Where the road 'hairpins' about halfway, is the top of the hill, the 'main' park and the location of Sullivan's Monument.  At the end of the road is the 'North Park.'

See map below for a close-up of the road leading to the top of the hill.