Creating an account on the Zotero website allows you to keep a copy of your library on the Zotero server, which is very handy if you do not always use the same computer or if you want to work collaboratively.
After creating your account, enter your username and password in your Zotero Preferences: Preferences menu, then Sync., enter your username and password. You will need to repeat this process on each of your computers. Any change made to your database will be automatically synchronised.
You can synchronise an unlimited number of references, notes, and collections. PDFs and other attachments take up storage space, which is limited to 300 MB for free. You can purchase additional storage space if necessary.
If you want to save money you can: