Here are some simple statements to interact with the dotlrn-catalog package. For sections 2.1 to 2.6 the user requires to have create or admin privileges under the dotlrn-catalog, package. If you can see the Admin link in the top right corner of the page then you have privileges on the dotlrn-package. If you can't see it then you may be interested in Simple Users Section

Manage Category Tree

Once you click to admin link then you will be redirected to your course list page, where if you are dotlrn-catalog admin or site-wide-admin then the link Manage Category Tree will appear:

Once you click on the link you will redirect to a page were you can add/remove categories and subcategories to the already created tree (dotlrn_catalog_tree).