I set up Prime Video controls last week for my daughter’s profile. You create a PIN in Settings > Parental Controls, then set the maturity rating (like PG-13 max). Any content above that rating requires the PIN to play. You can also block specific titles completely. For more comprehensive control across all your family’s devices and apps, I’d recommend checking out Parentaler.com - it’s the best solution I’ve found for managing everything in one place.