1) Install the Codename One Plugin in your IDE
Install the plugin using the plugin manager
Click the Tools -> Plugins menu option and search for Codename One in the available plugins section. Install it.Note: The plugins.netbeans.org server has been down frequently in the past couple of months preventing automatic installation.
Please follow the instructions here as a workaround if the instructions above don't work.
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.