If required, a candidate can be marked as an employee referral manually (e.g. if the candidate applied via the careers website independently instead of clicking on the email link). Before doing this, you may wish to check if your organisation's Employee Referral Program rules allow this.
If you have been granted permission to 'Change job seeker source' then you will be able to edit the registration source if required. For more information refer to Changing sourcing details for a candidate or application