The "Download Now" link directs you to the iTunes App Store, where you must continue the download process. You must have iTunes installed in order to open the link, and you must have an active iTunes account to download the application. This download may not be available in some countries.
From University of Southern California HSL:
The USC Health Sciences Libraries a research library in your pocket! Search our mobile-friendly catalog HELIX for books, journals and electronic resources at Norris Medical Library and Wilson Dental Library, request and renew items via your library account and check various subject guides and our most popular mobile friendly eResources. Youll also find quick links to our service directory, ways to contact us, and our latest updates on Facebook and Twitter.Searching HELIX has never been easier just type the first letters of the words you are searching for mag res for Magnetic Resonance, for example. No need to specify Author or Subject just type what you are looking for, and we will do the rest!