Jenkins has the Gerrit Plugin in place so that when we do check-ins to Gerrit, Jenkins performs a build and if it succeed
To copy an existing job, go to http://your-jenkins/newJob and use the "Copy existing job" option. Enter the name of the existing job - Jenkins will verify whether it exists.
The default tab on the front page of Jenkins should list all existing jobs, but maybe your predecessor deleted the tab. You can create a new tab listing all jobs from http://your-jenkins/newView.