how to "Make sure you have the Groovy plugin enabled"?

The docs on this page "Building and Running from the IDE":
http://www.jetbrains.org/pages/viewpage.action?pageId=983225

READ:
To develop IntelliJ IDEA, you can use either IntelliJ IDEA Community  Edition or IntelliJ IDEA Ultimate. To build and run the code:

• Make sure you have the Groovy plugin enabled. Parts of IntelliJ  IDEA are written in Groovy, and you will get compilation errors if you  don't have the plugin enabled.

What does this mean?

When i try to make the project i get:
"package org.jetbrains.groovy.compiler.rt does not exist"

so Im sure I have not completed that step.  How do i complete that step?

Thanks

-- edit --
When i do "which groovy" i get:
/usr/bin/groovy

so groovy is installed.

-- edit  edit --

oops sorry, this was supposed to be posted in the IDEA forums, not the phpstorm forums.