The help for this type of badge states:
You must have a total score of 100 in at least 20 non-community wiki answers to achieve this badge
So what does that mean exactly? How do I earn one?
These Tag Badges are for the number of votes you accrue on your answers a particular Tag. The instructions just set out how answers you need and how many votes you need between them.
In this case, 20 questions with at least +100 votes between them.