Go to the iTunes App Store
Tap the Download Bookshelf button to be taken to the Bookshelf download page in the iTunes App Store.
Tap the Free button, then tap the Install button. You may be prompted to sign in with your Apple ID.
For Assistance with your Apple ID please visit the My Apple ID Support Page.
Once Bookshelf has been installed on your iPad, iPhone, or iPod Touch, tap on the Bookshelf icon to launch Bookshelf. Sign in with your Bookshelf ID and password.