how to add menu item from tags? I am new in Drupal,
and I am creating  a library the library has subject, each subject select from a list that referenced to a taxonomy. 


  I want each subject become an item in my menu and when click on it
  show that tag result.
I'll post my comment here as an answer also so this question can be closed.

If you want a taxonomy vocabulary and it's terms to be represented in a menu you can use the module Taxonomy menu. It synchronizes changes in your taxonomy tree to a menu of your choice. 


  Transforms your taxonomy vocabularies into menus with ease!