Installing Mu on macOS is super easy.
Mu will run on any machine running macOS version 10.13 High Sierra or later. There is advice on Apple’s website on how to check your macOS version.
The following (silent) video demonstrates this process on Mac OS Catalina:
When you open the installer you’ll be asked to accept the software license agreement and then your computer will verify the package is not corrupted (this may take a couple of minutes).
Mu will install into the Applications folder on your Mac.
Press the CTRL button and click on the Mu icon. You’ll see a dialog to check you want to open Mu. Click “Open”:
This can take some time as OSX checks the Mu package, but you’ll only ever have to do it once.
Updates to the way OSX works means that when you open Mu for the first time you need to tell your operating system that you trust the application. The simple solution is to CTRL-click the Mu application in your "Applications" folder and then select "Open". If you don't you'll just see a warning pop-up (shown in the video at the top of this page).
If you're running Catalina then you might have to give the app permission to access USB mounted devices. To do that: