You have to create a mobileconfig profile and install it.this looks confusing , i have to download the imazing app?
The mobileconfig profile can be created with
Apple Configurator (made by Apple) https://apps.apple.com/app/id1037126344
iMazing Profile Editor (free, recommended) https://apps.apple.com/app/id1487860882
iMazing - “Create or edit Configuration Profiles for iOS, macOS, tvOS, or watchOS”
https://imazing.com/guides/how-to-create-or-edit-apple-configuration-profiles
ProfileCreator (free) https://github.com/ProfileCreator/ProfileCreator
If you don’t want to install an app, you can copy-paste the text (Code:..) from the first post in TextEdit (Format – Make Plain Text) and save as Defer90.mobileconfig