It's important to understand what your C-suite wants and needs from PMM. Product Marketing is a versatile role and often looks different at every company, and you need to be somewhat flexible in what you focus on based on company goals.
But with that said, it's important to establish the core charter early on - and one way to do that with the executive team is to use examples of how PMM works at other (similar companies) and highlight why you believe it should be that way.