How do I assign an SLA instance to contact records using Data Import Wizard or the APIs?
In order to assign an SLA instance to a contact record created from these sources, you will first need to create a business rule having an action to create an SLA instance (an active SLA). When that rule is triggered the SLA instance will be associated with the contact.
Please note that in order to have the SLA added when importing contacts, the option "Run Workflow Rules" should be checked in the Data Import Wizard.
It is not possible to associate SLAs by defining them within the Data Import Wizard CSV file or to set/update SLA instances through an APIs request.