You can start with this:
- SAP PO/BPMN course getting your be ready to create first
- SAP Process Orchestration. The Comprehensive Guide of John Mutumba Bilay, Roberto Viana Blanco - by SAP PRESS
- BIT800 - Process Orchestration Overview | SAP Training and Certification Shop
- SAPBPM - SAP Business Process Management | SAP Training and Certification Shop
- Introduction to SAP Process Orchestration
- SAP Process Orchestration Video Tutorial: How to use the reliable connectivity using BPM and PI - YouTube
- SAP PI iFlow Demo - YouTube
Best regards.