The ThreatX portal allows you to easily block an IP Address or a CIDR range by adding it to blacklist.
As first step you will have to log into the ThreatX portal at x.threatx.io and access
Settings > IWAF from the navbar.
Select the Blacklist tab and click on Add Entry in the top right corner.
This will present you with a pop to add the IP address or the CIDR range. Add and click Submit.
If you are blacklisting an entry previously in the whitelist make sure that you remove it from the whitelist.