How to setup the Permissions by Term module in drupal 7?

In the module page the author suggested to
add 1 more field that has to be a “taxonomy term relation”
and should have the following machine name for this field: “field_secured_areas”.

The problem is where will I add a field? and what does he mean when it has to be a “taxonomy term relation”?

Thank you.

Drupal version: 


Source: https://www.drupal.org/taxonomy/term/22/feed