Adding Terms to Levels
All terms in levels below the top level must be related to a term in the next higher level.
You must begin by defining at least one term in the highest level. You can then add terms related to that term (child terms) in the second level, and then define child terms for those terms in the third level, and so on.
Note:
You can add terms only to active hierarchies. See Activating the Hierarchy and Making it Usable or Unusable.To add terms to classification hierarchy levels, go to the Terms subtab of the Classifications tab and do the following:
Parent topic: Creating and Maintaining Hierarchies