Open Settings
Tap Screen Time
Tap Content & Privacy Restrictions
Turn on Content & Privacy Restrictions
Tap Content Restrictions
Tap Web Content
Select Limit Adult Websites
Under Never Allow, tap Add Website
Enter the website address
Tap Done
To block all websites except approved ones, select Allowed Websites Only
Tap Add Website to add approved sites
Enter the website address
Tap Done
To remove a blocked website, go to Never Allow
Swipe left on the website
Tap Delete
To prevent changes, set a Screen Time passcode
Go to Screen Time
Tap Use Screen Time Passcode
Enter a passcode
Confirm the passcode