Navigate to where you would like to save the backup file. Best to save to the desktop
You can then cut / paste / move the file to your backup location: USB, backup folder.

In the File name: field enter a NEW name for your library. The best option is to use your original library name and append the date on the end. For example: MyLibraryName070318. This way you will know which library the backup refers to and when the backup was made. Using exactly the same name for a backup as the current library can mean that you may overwrite current data with old data!

The file will be saved at the required destination.

If you ever need to use the backup file:

Copy the file back to your computer to a location such as your documents folder.
Double click on the file or open EndNote and select File Menu>Open>Open Library and browse to the file.
2 files will me created at the same location as the backup file:
MyLibraryName.enl ( This is the main library file )
MyLibraryName.Data ( This folder contains the library data structure and attached files, images, PDFs etc. )

If you ever decide to move the library file (.enl) away from this location you have to move the corresponding (.Data) folder along with it. The compressed library feature, compresses, zips, all the files into one which you can easily move to a new location.

Folder View

If your library exceeds 4.5GB then you will not be able to use the compressed library. Use the file > Save a Copy. Rename with a back-up name and save to the desktop. You will then need to copy both the new .enl and .Data folder to a back-up location. Keep the .enl and .Data folder in the same location. Make sure you have enough space on the back-up USB or folder location.

Remember to save your Word documents using the same method of appending the current date. Simply pressing the save button overwrites the older version. If your document has an error using the save feature will save the error on top of a working file.

Using the Save As option and appending the date means that you will have a working backup document if anything should happen to the original.