What is a IntelliJ IDEA?
IntelliJ IDEA is an IDE, or Integrated Development Environment, by JetBrains. It attempts to integrate all of the development tools that you might need into one single place.
There is a Community Edition that is available for a free download
Choose the Mac OSX tab and click the Download Community link
Open the .dmg folder and move the IDEA app into your applications folder.
Known installation issues
There are currently no reported issues. If you are having one, please report it in the Treehouse forum.