If you already have an ‘EndNote Online’ account you can supply the same email address and password when you registered for EndNote Online. Alternatively, click ' Enable Sync', then click ' Sign Up' to create an EndNote Online account.
In EndNote Desktop go to Edit > Preferences > Sync.
This will ensure your EndNote library is periodically saved online, avoiding any future loss of data. If you are using EndNote Desktop on a personal device (your own computer off-campus) you should ‘sync’ your Library using an ‘EndNote Online’ account. EndNote Desktop is not Web-based and stores references on your local computer.