Up to 50 total sites can be manually blocked at the network, person and device levels combined. IP addresses can only be blocked if you have Outbound IP Protection and Intrusion Prevention enabled.
Blocking a Website for Everyone
Tap on the Guard tab inside the main menu.
Tap on Manage security events.
Go to Block and then tap on Block... on iOS or the + if you are using Android.
Choose either Block website or Block IP Address.
Based on your previous choice, enter the URL or IP Address you wish to block. Please note that the full domain name is required for websites. For example; make sure to write "youtube.com" instead of "youtube".
Tap on Block to confirm