In order to enable Omnisphere Library Integration, you must have Keyscape registered in your Spectrasonics User Account and installed on your system.
If you already have Omnisphere on your system, you will be asked to reauthorize it after you have installed and registered Keyscape. When you launch Omnisphere, you will see the following splash screen. Click the AUTHORIZE button, and follow the usual steps for authorization.
After (re)authorizing Omnisphere, the Keyscape libraries will appear in your Omnisphere Browsers.