On the library's home page, use the Databases link just below the search box, then search for 'hathi'. You'll get a link to the HathiTrust database.
All items in HathiTrust are fully indexed in Discovery. Discovery will link to public domain (out-of-copyright) items directly. Items still in-copyright that match an item in our print collection are full-text searchable and Discovery Search will link to the print record in the catalog.
Please see the Research Guide on HathiTrust page for further help and information.