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 URL
Tap Done
To block all websites except approved ones, select Allowed Websites Only
Under Allowed Websites, add the sites you want to permit
To remove a blocked site, go to Never Allow and delete it
If prompted, set a Screen Time passcode to prevent changes