The easiest way is to get a good parental control app, like Qustodio, which is the best parental control app for iOS. It allows you to filter websites by predefined categories, whitelist and blacklist sites, and block unsupported browsers. Your kids also won’t be able to use incognito mode or a VPN to get around your restrictions either.
Once you pick a parental control app for iOS, you should follow these steps: download and install the app on your phone and your kid’s phone and set up the rules and restrictions you want to enforce on your child’s phone.