PostProc is part of the QUANTUM ESPRESSO distribution and depends upon PWscf for compilation. For instruction on how to download and compile QUANTUM ESPRESSO, please refer to the general Users' Guide, available in file Doc/user_guide.pdf under the main QUANTUM ESPRESSO directory, or in web site http://www.quantum-espresso.org.
Once QUANTUM ESPRESSO is correctly configured, PostProc can be compiled by just typing make pp, from the main QUANTUM ESPRESSO directory; or typing make from the PP/ subdirectory. Several executable codes are produced in PP/bin and linked to bin/.