From I-376, take the Edgewood exit (number 77) and follow S. Braddock Ave, going north.  At the first traffic light, turn left onto W. Hutchinson Ave.  After four blocks, at the intersection with Lancaster Ave, a sign saying "Frick Park" is visible with a road to the right, descending into the park.  Take the road into the park and follow the red and white orienteering signs to parking. 

Here is a Google maps link to where you turn into the park

The GPS coordinates for the park entrance are  40.431246 N, 79.898078 W