NOTE, If you are using PowerTeacher Pro (non Java gradebook): 

>>>>> Click here for instructions  <<<<<

Otherwise follow these:

First, click "Installer":

Then click "Download Installer":

Next, open the .dmg that downloads:

Double click the installer:

Click "Open" if this message appears:

Click "Run":

Click "Okay":

Click "Launch":

Open the .ptg file that downloads:

You only need to do this once on each machine you use PowerSchool on. After that you can launch it with the desktop icon: