Can't follow the instructions from the readme file. There is no such menu options as described in the readme in Intellij: IntelliJ IDEA→Preferences...→Other Settings→google-java-format Settings on macOS
Also no such menu path:
To enable it by default in new projects, use File→Other Settings→Default Settings....
Once more, there is no such path:
To use the plugin, go to Help→Edit Custom VM Options...