There is currently ongoing free online training by SAP @ https://open.sap.com/courses/byd3/items/1AmQcfJ1RHVJptxP1fK6Pj
This course is on SAP BYD accounting and it has very good content. More then 4000 thousand people have subscribed and you will get a free access to SAP BYD system from the course.
Week 1: Introduction to SAP Business ByDesign
Week 2: Goods and Services Value Chain
Week 3: Monetary Value Chain (Part 1)
Week 4: Monetary Value Chain (Part 2)
Week 5: Period-End Closing
Week 6: Final Exam
Duration: 5 weeks (3-4 hours per week)
So go ahead and get started in ByDesign by joining that course.