Perhaps they are higher up in the org chart, but what does that matter?
Your PO is not your parent and you shouldn't assume a parent/child relationship. They are your team member in producing high quality software. Sure they might have different responsibilities, but you're all professionals and experts in your own domains. Treat each other as such.
- Don't be afraid to ask them questions.
- Don't be afraid of making mistakes or taking risks
- Don't be afraid of challenging them.
- Don't be afraid of telling them when they aren't doing what they need to be doing to help the team.
- Don't be afraid to tell them if their actions are detrimental to the team.
Try not to be afraid. If you are, recognise it and then push through. Work together as professionals.