iTunes 12 home sharing import album
Home Sharing is a method to share music directly between Mac's on a local network authenticated with the same iTunes account.

Family Sharing is the method for sharing purchases made through iTunes or App Store by a defined group of iTunes accounts all using the same credit card.

Share My Library is a preference in iTunes that allows local network user to stream, but not copy, music from your library. 

The Home Sharing feature allows one to view, copy, and play music from a locally networked Mac. In iTunes 11 and earlier, it was relatively simple to drag content over to your own library and thus copy the files over the local network. With iTunes 12 it can be a bit less obvious. 

With a properly configured pair of Macs on Home Sharing, you can drag a song to the left and a sidebar will reveal allowing you to pick a target location. This function is often broken and requires you unconfigure/reconfigure the Home Sharing. 

See this Apple Discussions thread for more details.