By adding existing extensions
Check what exist and you may pick-up some in this list of published extensions and install them as documented.
By writing your own extension
The Datamodel customization explains how to extend (or modify) the data model of the application
Examples of How to :
Customizing the Portal
2_3_0/customization/start.txt · Last modified: 2016/10/10 11:22 (external edit)