If you have chosen an attribute with the data type of Code table, this field will be edited in Administration > Code Tables. You will need the Code Tables System role to view these filters. 
  1. From Administration, Click Code Tables
  2. Choose adjust the filters to use the Category Attributes
  3. Click the Code Table name you would like to edit
    1. To Add new fields, Click Add
    2. To Edit existing entries, Click the arrow to the left of the entry, Click Edit