A custom referral source can be created in patient demographics either while creating a new patient...
or from the patient demographics in the individual patient history. Use the + sign to the right of the Referral source field to manage your referral source list across your entire account, not for just this specific patient.
Choose the category for your referral source and add a custom referral source by using the + sign.
Name the referral source and click Add.
The referral source will be added to the list. Select the checkbox to activate the referral source.
Click on the pencil icon to edit and the 
icon to archive the custom referral source.