Learn the basics of MoveData customisation in this example where we add logic to set the field Contact.LeadSource to Web:
Additional notes to accompany the video:
In this example the Record variable references the Contact object. You could easily apply the same logic to Donations by passing in the Opportunity object instead, and repeat this pattern for other core objects in Salesforce (Account, Contact, Campaign, Recurring Donation, Opportunity).
It is best practice to add your field to the field set each time - this will print information on that field to the execution log - but in practice, the integration will only error if a field has not been added to a field set and you are undertaking a decision against that field.
In the vast majority of cases your customisation logic will be an extension of the object Mapping flow. The below table may come in handy if you are trying to work out which mapping flow to clone in the MoveData Pipeline: