How to incorporate actuals for prior months into forecast scenario in EPBCS workforce

Use case: For a POC, I need to track employee hiring in workforce: actuals compared to plan and forecast. Just workforce module is configured.

I need to find out how to seed a forecast scenario to contain prior month actuals and plan data for future months, before users start to work on the forecast. Would appreciate link to documentation on step-by-step actions to take or which predefined rule/s, data map/s to run -I could not find any.

Thank you.