To create Custom Data Fields in Salesforce follow this steps.
1. Go to module mapping and choose Unmapped Fields
2. You will open a window where you can map fields that weren’t automated. Where target fields are press Add Custom Field
3. A window will open where you can create a custom field. Enter the Label and Name of the custom field.
4. Choose a field type on your target CRM from the dropdown list.
5. After filling in the required fields press Add Custom Field
6. The custom field will appear in the list so you can match it.
Please note that this option is available only for Accounts, Calls, Contacts, Events, Leads, Opportunities, Tasks, Opportunities.
In case you don’t see created custom field in Salesforce, see “What To Do if the Created Custom Field Doesn’t Show up in Salesforce?”.