Options include

Nightly: Imports run from uploaded files created from reporting either manually through Admin Settings or automatically from a Windows schedule on the Server.
API: Imports run using direct connection to an external system by a scheduled process. Currently, the only import configured in this way is the PrismHR API. For assistance, log an Extranet case.
Scheduled Process: Imports run from the Process Scheduled Imports scheduled process. Files in Ready for Import status are automatically imported when the scheduled process kicks off.