- Create a new namespace and use that to create custom properties to map to these new fields
- Edit the OOTB metadata schema to add these properties to the schema
- Apply the metadata schema to a particular folder where you would need these new properties
- Now, when you do a metadata import, the properties will be automatically mapped to the assets. Just make sure the name of the properties in the import step matches what you created in step 1
See [1] for more details
[1] https://experienceleague.adobe.com/docs/experience-manager-65/assets/administer/metadata-schemas.htm...