Syncing your library means backing up your citations on Zotero's server. This way you can access your citation remotely and retrieve them if something happens to your personal computer.

In Zotero 7 Standalone, you will see a green arrow on the right side of your application. If you click on it, it will spin to indicate that it is uploading your citations.

Follow the instructions below to sync your library. 

1. Open Zotero 7 Standalone. 
2. Click on Zotero and then Settings (Mac) or Edit and then Settings (PC) and select the "Sync" tab.  
3. Enter your Zotero user name and password. 
4. Check the "Sync Automatically" box and click "Ok." Zotero will upload your library to the server. 
   • You will see other options allowing you to sync attachments and full-text content, which you can select at this time. 
5. Repeat this configuration on each of your computers.  Any updates you make on one of your computers will be reflected on the others.  This even works to synchronize your library among Windows, Mac Linux, and iOS devices.

If you're regularly using more than one computer in your research, Zotero's sync feature can keep your library up to date on all of them. Zotero can store a copy of your library on the Zotero.org server and check it for updates whenever you open your library on a different computer. All your computers must be running the same version Zotero and be configured to sync to the server.

For more details and help troubleshooting sync problems, check the Zotero site.