To download Oxygen for Mac, the project Github page:
Release 1.25.0 · oxygenhq/oxygen-ide
Click on the link for the DMG file. In the screenshot below that would be "oxygen-1.17.0-osx-x64.dmg"
After the file downloads, open the dmg file by double clicking it.
Click and drag the Oxygen icon to the shortcut icon for the Applications folder.
As detailed in the Oxygen CLI documentation page. you have to install the Oxygen framework from the Terminal in order to have the benefit of being able to execute Oxygen from test suites. (multiple sets of tests)
From the MacOS / Finder Spotlight Search, type Terminal.
A pre-requisite for installing Oxygen CLI and running it via the terminal, is having Node.js installed, which also includes NPM.