Installing IL2CPP Support, install location?

When trying to install IL2CPP Support, the installer doesn’t auto-select the destination folder to install to, it asks the user to select the destination folder location. Is this a one-time install for use in Unity anytime, or is this the kind of install that must be done for each project as needed? If per project, I assume I select the main project folder? If this is a one-time general install for Unity, then where do I tell it to install to?

Unity 2017.2x
Windows 10 Pro

It should automatically detect your Unity installation (I’m not sure why it wouldn’t - do you have a matching editor version installed?). It should be installed into the same folder as the editor.

How do you install IL2CPP Support?

Unity 2019.5.13f
Windows 10

Use Unity Hub.