To delete a list, select the list and then click the red Delete button that appears above the table. By default, this will not delete the contacts on the list; it will only delete the list itself.
After clicking Delete, a pop-up window will appear to confirm that you want to delete the list. There will also be a checkbox where you can select if you would like to delete the contacts on the list from the CRM. Click the checkbox if you would like to delete the contacts from the CRM, then click OK, or click Cancel to save the list. If you would like to delete multiple lists at once, select all the lists you wish to delete before clicking the Delete button.