To start a new Conversion Job, you have a few options: click the New button on the toolbar, select File\New Conversion Job from the menu, or simply press CTRL+N.
Please note: Starting a new conversion job will clear all existing items from your conversion task list. Ensure you have completed or saved any important tasks before proceeding with a new job.
See also:
Saving and Restoring a 'Conversion Job'
Creating a New 'Conversion Job'
Saving the Log as a 'Conversion Job'