You will need to be clear about both of your positions, where the responsibilities lie, setting out the approach the team will take, how the epics will be prioritised, broken down into stories and then further down into specific tasks. Explain the product backlog, why this needs to be reviewed and updated regularly. Make sure the Product Owner understands Scrum and specifically what is required of them. These changes are your joint responsibility. It's imperative that you both understand and agree the approach.