This plugin allows you to use CA Harvest as a SCM.
First things first - install the plugin, either through the Jenkins plugin administration, or manually.
Select Manage Jenkins from the main menu, then select Configure System from the options presented:
If the plugin was installed properly, you should find a section on this page for Harvest which looks like this:
Once the server settings are configured, new builds can choose it for pulling down code. Create a new build, give it a job name, and select the type of build (free-style, maven2, etc) and click OK. On the subsequent screen, you'll see a section called Source Code Management where you can select Harvest. Select Harvest, and the following options will appear: