Sometimes you need to add contact to a Pardot list. This can either be to mail them email on a standard basis (i.e: BI Updates, General Marketing, etc.) or to exclude them from a mailing (this is called an Exclusion list). To do so, simply locate the record inside Salesforce that you want to add to the list, scroll down to the "Pardot Email Marketing" section, and select the list to add the recipient to.
When marketing sends out the email, they will use the Exclusion list to remove anyone from the mailing that would prefer not to get one. If you manage to find a situation where a list is not visible, please contact the project manager of your department and they can work through that process.