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 DefenceJobs.gov.au:
Tying knots is a vital skill to have in the Royal Australian Navy. With this handy tool, learn to tie different Navy knots with 3D animated tutorials and facts.
Learning The Ropes - Navy Knots for iPhone
