This section will cover how to add a custom mapping to a subscription.
1. Select "ADD NEW MAPPING".
2. Select " Custom Field" as type of data source from left "Source" dropdown.
3. Select custom field attribute of data source from right "Source" dropdown.
4. Select " Custom Field" as type of data destination from left "Destination" dropdown.
5. Select custom field attribute of data Destination from right "Destination" dropdown.
6. Click "Save".
7: When are finish adding all mappings to a given collection, click the apply button at the bottom of the page.