When you open EndNote for the first time you will be prompted with three options:
‘Learn about EndNote’, ‘Create a New Library’ and ‘Open an Existing Library’.
Choose ‘Create a New Library’ and save it with a new, meaningful name to your hard drive.
Your new library will look similar to the the following screenshot:
EndNote reference management software, Clarivate Analytics, Version 20, 2020.
Your library consists of two files - the main library file which has a .enl extension and the data folder that has a .data extension. The data folder is automatically created by EndNote and is stored in the same location as the library file. The main function of the data folder is to store attachments. You must have both files together to open your library. Never delete the .data file. Back-up copies of your library must always include the data folder.