Go to Filtering > Allow & Block List and follow the steps below to add an allowed or blocked domain:
Select the Domains tab.
Select Add and choose Allow Domain or Block Domain.
Complete the fields in the pop up:
Domain to Allow/Block: Enter the domain you want to allow or block.
Include Subdomains: If your domain is example.com and you select this option, then all domains that end in example.com will also be allowed or blocked. For example, support.example.com and products.example.com.
Comments (optional): Optional comments about this allow or block domain.
Select Allow or Block.