Intellij IDEA provide two convenient ways to install plugin, you can download the plugin from repository page and install by yourself after you get a local copy. Another way is install directly from the repository. Both you need click “Intellij IDEA -> Preferences -> Plugins(IDE Settings, left panel)”.
In the first screen, you can select “Install plugin from disk…” to install the plugin you downloaded, that is the first way. You can also select “Browse repositories…” to go to second screen and search for “p4intellij” and click “install”.
This Plugin is compiled by JDK 7.0, so you need to run your Intellij on JDK 7.0.
For Mac user, there are some default problems that Intellij can not run JDK7.0, below is the way to fix:
1) Upgrade your JRE to 7.0;