For Psychopy, most will simply want to download the .dmg of the executable.
Developers can install a local version of the repository using github. See the instructions at the online psychopy documentation "for developers" section.
This requires installation of the python library dependencies. Once that is all done, execute psychopy in the terminal with something like
Rather than type that every time, create an alias, maybe called 'pp', by adding a line to your ~/.profile like this:alias pp='python /Users/alex/Documents/softwareStatsEquipment/programming_psychophysics/psychopy/psychopy/app/psychopyApp.py'