how to configure data masking for additional delivered components/ records/ fields

We are working on setting up data masking and it works fine on the delivered configurations, but I need to be able to add configurations to component/records that were not delivered.

When I read about it I see the following line, which implies that it can be modified, but I am not sure where. 

Note:

The Record and Field storing sensitive information is pre-configured as system data, and is read only. Masking format can be modified for Field Groups- Date of Birth and National ID. Associated Fields are pre-configured for a few of the delivered components. This can be modified.