Greetings!
Couple of simple ways to block websites:
1) add the URL to your HOSTS file at "C:\Windows\System32\drivers\etc" which doesn't use Comodo at all.
Don't forget to write it like this:
127.0.0.1 <URL>
2) add the URL to firewall/common tasks/my blocked network zones in CFP3
It won't work. You can only add IP, MAC or hostname. If you want to block just a specific website, use the HOSTS-file. If you want to block multiply websites, Comodo isn't made for that. Better use some other software that supports keywords and wildcards.
Cheers,
Ragwing