In the class AbstractDesktop you can overwrite the method getConfiguredOutlines() to add your Outlines. If you want the creation and adding of an Outline in one go you can use the Scout Perspective:
In the Scout Explorer navigate to your client package which has a child called "Desktop". On its child node "Outlines" is a context menu "New Outline..." which guides you through the process.
(Correction: Changed getConfiguredDesktops() to getConfiguredOutlines()...)