Led Help Centers for advertising products at Google. Helps B2B SaaS companies with product management and customer support. Partner at software, UX and strategy consulting company.
I did it gradually by beginning to do the things product managers I worked with did. One task and skill at a time while I was in a role in an adjacent team. That also helped me see which skills were transferable, in some cases skills other product managers didn't have.
What those skills and tasks are depends how you define the product manager role you want. Product Management can mean many different things depending which industry and company you're in. It covers a broad spectrum from deeply technical roles to more marketing and sales oriented ones.