To use Zotero you must first create a Zotero account:
Go to the Zotero.org website then click on Log in on the top right corner of the page.
Select 'Register for a free account' and follow the onscreen instructions to create a Zotero account.
Once you have done this, Zotero will send you an email message asking you to authenticate. Click on this link and authenticate.
Zotero allows you to register multiple email addresses (under Settings/Account).
One of the email addresses needs to be the primary email address.
If you are being provided cloud storage space on Zotero by your UCL faculty, make sure you set up your Zotero account with your UCL email address as the primary address and notify your librarian. Otherwise, make your personal email the primary address so that you have continued access to your Zotero library after you leave UCL.
You can only have one Zotero library associated with your Zotero account. You can, however, have as many folders as you want on Zotero. You can also add your own tags and connect ('relate') references on Zotero.