1. Download and install IntelliJ IDEA
Download and install either IntelliJ IDEA Ultimate or IntelliJ IDEA Community Edition.
2. Check out Community Edition source files
3. Configure SDK and source files
Configure a common JDK and an IntelliJ IDEA Plugin SDK. For IntelliJ IDEA Plugin SDK you should specify the directory with installed IntelliJ IDEA. By default it offers the directory of the currently running IntelliJ IDEA.
To attach the Community Edition source files to the SDK, open the Sourcepath tab in the SDK configuration dialog, press the Add button and select the directory with the Community Edition source checkout. IntelliJ IDEA will scan the directory for roots and offer the list of roots to add, with everything checked by default. Accept the list of roots by pressing OK.
4. Install additional plugins
Install and enable Plugin DevKit, Grammar-Kit and PsiViewer plugins.
5. Create a project
Create an IntelliJ IDEA Plugin project and specify IntelliJ IDEA Plugin SDK.
