Content cannot be shared from one library to another unless the source library has permission to publish to the destination’s shared library. You can also allow another Library to publish straight to one of your playlists using Direct Publishing.
To allow content to be placed in the Shared Library, first browse to the library that will be shared to.
Once there, click the Administration button in the navigation pane. Click Library, then select the Sharing option.
In the Sharing window, you select one or more libraries, which will have permission to publish to your shared library.
When the desired libraries are selected, click Add to My Shares. You will then be returned to the main Sharing menu, where you can also allow another library to Copy or Transfer content.
In this example, the library titled Ensemble Video can send content to this library's Shared Library. The library titled iTunes can send content to the Shared Library, AND copy content directly to the Media Library.
To learn how users can publish to a shared library once sharing is enabled, visit the Publishing and Sharing guide.