The releases are available at the PATRIC3 github site.
Download the latest version of the PATRIC dmg (disk image) file. Click on the downloaded file to open it, and drag the PATRIC icon on to the Application folder icon. This will install into your Applications folder.
Then doubleclick on the PATRIC icon in the Applications folder. This will bring up a new Terminal window that is configured for access to the PATRIC command line tools.