Use Groups to share references with other Zotero users online. It's a great way to work on collaborative research projects.
To create a shared library, click the Create Groups button near the top left of your Zotero window (small blue/green button with two “people” icons, second from the left).
Next, click the Member Settings tab
To join an existing Zotero library, search for it at https://www.zotero.org/search/type/group or be invited by the group’s owner.
After you create groups, you will have two sections in your Zotero collections pane: My Library and Group Libraries.
Personal and group libraries are entirely separate, and changes made to items in one library do not affect the other. You can drag items back and forth libraries to copy items.