EndNote automatically saves references as you add them to your Library so you do not need to save your library each time you exit the program. However, it is advisable to save a back up library in a separate location (such as to a USB) so that you don't lose all your work if you encounter issues with the program or your computer.
Do not save your working EndNote Library into cloud-syncing folders such as iCloud, OneDrive, Google Drive, Dropbox etc. Saving to cloud services can corrupt your library over time.
To save a compressed library file in your USB:
Clicking on the saved library (has an .enlx file extension indicating that it is a compressed library) will split it to an .enl file (uncompressed library) and the .Data folder.
When saving your library it will be useful to include the date the backup was done e.g. Sample library backup 010219. For subsequent backups, overwrite the previous backup library with the new date.
You have your main library on your home computer. You are now at University and you have added some references into another EndNote library. Save this new library as a compressed file to your USB.
Back on your home computer you can merge this library on the USB into your main home library. Open the .enlx file on your USB (this will split into a .enl library and a .Data folder).
To merge both libraries: