Please ensure that you have created a Mapping Set so that you will be able to map data from the Smart Form to and from Salesforce. Please see this article for more information: How to use Smart Form Mapping – Create Mapping Set
Edit an Element
1. Open up the Edit Properties Window for the element and navigate to the Mapping tab.
2. For Mapping, you will be able to view the mapping configurations already created for the current form and a mapping data set.
3. Under Element Mapping Details, using the radio button options, you can exclude the element from the mapping, or you can map the element based on the mapping configuration you have created.
Select the Map to and from Form Response radio button. To set the mapping to, from, or to and from a Salesforce object. You will need to type in the correct mapping syntax.
For a quick and efficient way to do this, make sure to use the Mapping Lookup tool: Mapping an Element with the Mapping Lookup tool
Mapping syntax is structured as the following once inserted:
Referencing a Field from the Object Record running the Form
For a field of the Object record running the Form, use the API Name of the field followed by a colon ':' and then the API Name of the Object running the form.
If the form is running on a Work Order and you want an element to map to/from the Subject field of the Work Order, you'd use 'Subject:WorkOrder' as the mapping value. If the target field is a custom field, that means including the '__c' postfix of the API Name, e.g. 'Building__c:WorkOrder'.
Referencing a Field linked through a Lookup Relationship from the Object running the Form
For a field that is one level deeper than the object running the Form, i.e. linked to the object record via a lookup field, use the API Name of the lookup field followed by a '.' and then the API Name of the target field.
If the form is running on a Work Order and you want an element to map to the 'Phone' field of the Contact assigned to the Work Order, you'd use 'Contact.Phone:Contact' as the mapping value. If the lookup field is a custom field, that means including the '__r' postfix of with the API Name of the lookup field, e.g. 'Contact__r.TemporaryLocation__c:Contact__c'.
Select Save to finish.
Please see this article for more information on a mapping object model for the Work Order Object: Syntax for Mapping Elements with Record Fields