You can navigate in the alphabetical list or directly in the tree view using + and - to unfold and fold tree branches.
Select a term by checking the box on the same line. Extend search (autoposting) with ++ button.
On bottom of request window, check the box to add synonyms to the request.
Press "Request" to send request to 3 search engines simultaneously (Yahoo, Google et MSN). Results will be shown in a new window you can close to go back to the thesaurus.