1 - Create and activate the case-acknowledgement email....
2 - Create a new business process flow record for the case entity.
3 - Create and activate the process flow with each of the stages....
Reference:
https://docs.microsoft.com/en-us/dynamics365/customer-engagement/customize/create-business-process-flow
https://docs.microsoft.com/en-us/dynamics365/customer-engagement/customize/workflow-processes