Close all Microsoft Office related Programs including Outlook.
II. Create your EndNote Library
Open EndNote
From the File menu, select New
In the New Reference Library menu box
Go to File name and give your library a name of your choice
Go to Save as type and make sure to read: EndNote Library.(*enl)
Click the Save button to save your library. A plain library with no references will open.
Once created your EndNote Library consists of two files: 1. The .enl file (e.g. My EndNote Library.enl)
2. The .data file (e.g. My EndNote Library.data) which will have the same name and will stores all your PDFs. Make sure to keep these two files together if you want to save a backup copy or email a copy of your EndNote Library.
Recommendations
Create only ONE EndNote Library and use Groups to organize your references.
Do NOT Save your EndNote Library to the cloud synching folders such as Dropbox or Google Drive.
Back up your EndNote Library regularly. Making backups is necessary and can be done easily: go to the File menu and select Compressed Library (.enlx). This will automatically save both files (.enl file and .data file)