I have Drupal 6.2. I added a taxonomy term and I am trying to to add it as a new field to a content type. However, I don't see "taxonomy term" as a "type of data to store" when I try to select a field type.
Use the Content taxonomy module. It provides a CCK field type for referencing taxonomy terms.
Visit the Taxonomy administrative page (admin/content/taxonomy), and click on the "edit vocabulary" link for the vocabulary you want to associate with a content type.
On that page, you find the "Content types" field set that allows you to associate the content type for which a vocabulary should be used.