Warning: You are advised NOT to click on the link to sign in via your institution, organization or Athens. UCL does not have an institutional subscription to Mendeley and there are issues with users being unable to log in to Mendeley if they have created an account through this route.
Follow the on-screen instructions to complete your registration and create a Mendeley Web account. Using your personal email address will mean you will still be able to use the Mendeley account when you have left UCL.
You can only have one Mendeley library associated with your Mendeley account. You can organise your references using collections or tags if you wish to work with a subset of references from your library.