There are 6 ways to get references into your EndNote library
This feature was introduced with EndNote X2 and has been further refined since then. You can select one or more references, a group, or your entire library and have EndNote scan for full text available to you. When the full text is found, EndNote downloads and links it to the appropriate reference automatically as a File Attachment. To run this feature go to References > Find Full Text.
This function will only work for free journal articles (open access).