1. Use the Sitemap to navigate to Salesforce then Configuration and select Field Mapping.
2. Click Create a new mapping set.
3. Enter a Name for the field mapping set.
4. Enter a Description of the field mapping set.
5. Click OK.
6. Click Salesforce Marketing Cloud Fields.
7. In the new window that appears, click AddField.
8. In the Fields section, enter the attribute to send in the data extension. Provide a name for the attribute and specify the type, length, and precision.
9. Click Add Field.
10. Save and close.