A free online Zotero account allows you to sync and access your library from anywhere, back-up your attached files, as well as share citations.
From your desktop version of Zotero, go to Preferences>Sync>Create Account>Set Up Syncing to set up a user name and password. Then check the sync automatically box and both file syncing boxes.
Once you have set up your online account, click the green circular arrow button in the upper right corner and Zotero will sync your local library with their online server. To access your library online, go to www.zotero.org and and log in to your account.
From your online library at www.zotero.rog, you should be able to see the collections and citations from your local Zotero library. You can share sources from your online Zotero library with other Zotero users.
To create a group, click on the Groups tab in your online Zotero library. Click Create a New Group, give it a name, and choose a group type.
Decide what type of access to give group members. This is an important consideration; full privileges allow group members to add and delete citations in the shared library.
Once you have entered membership settings, invite users to join your group: Member Settings>Send More Invitations> e-mail addresses
As members add citations to the group’s online library, you can view them by clicking on the Groups tab and then clicking the Group Library link. After syncing your Zotero account, you will see your shared groups below your personal collections in you local standalone library.