1) Install the Codename One Plugin to your IDE
IntelliJ IDEA Installation
Download & install Java 8. Notice that while Java 7 will work with other IDE's we no longer support it for IntelliJ!
Download & install IntelliJ/IDEA, notice that Android Studio will not work.
Install the plugin using The Plugin Center
Use the search functionality in the plugin center to find and install the Codename One plugin.