Setting your Find Full Text preferences will enable you to download and attach PDF files to references in your library.
The first time you use 'Find Full Text' in your EndNote session you will be asked to Authenticate your account.
Go to References > Find Full Text > Authenticate. You will be prompted to log in with your MQ OneID & Password.
After Authentication
A: Find Full-text works well, but not perfectly. Reasons why include
Publisher's website does not support or allow this functionality.
Too many users are already in a database with limited access.
Journal handles letters, editorials, & other genres differently, making it difficult for EndNote to find the citation.
Article is buried in a large full-text database that does not allow individual articles to be easily retrieved.
If you have had a few failed attempts at using the Find Full-text on a particular reference, then add the article manually to the reference i.e. download the PDF and attach it to the reference.