Go to https://access.clarivate.com/login?app=endnote Click on Register.
Fill out the form.
This is done in EndNote on your desktop, not online.
Use the "Setting EndNote up with Preferences" page to set up your preferences to sync your library.
You can share your entire library or only a specific group within your library.
It is important to note that the attachments to your records will not be shared with anyone due to copyright concerns.
EndNote.com has a guide for sharing for more information.