This article describes how to block/allow domains on Android. For iOS check this article.
The easiest way to do add domains to Ad blocking / Blocked Hosts or Allowed Host is to search the Host log (which is a submenu of Ad blocking) for the domain you want to add. Tap on it and either tap ‘block’ or ‘allow’.
If you want to manually enter a domain in one of those menus be sure to follow this format:
example.com
You can also add the same domain with a ‘www.’ in the beginning. In prior versions this helped blocking the domain. Use this format:
www.example.com
You can also enter domains with a subdomain. Be sure to follow this format:
adserver1.example.com
www.adserver2.example.com
Do NOT include the protocol (e.g. http:// or https://) or the the rest of a link (e.g. /download/v42). Remember Blokada blocks whole (sub)domains.
If you face problems blocking or allowing a domain be sure to check out this guide as well.
This image shows what to add to Blocked Hosts or Allowed Hosts