For EndNote X1 and later, you can simply download the demo version from this site. During installation, choose "I am an EndNote customer" in EndNote X6 and earlier versions or "I have a Product Key" in EndNote X7 or later. You will be prompted to enter your Product Key and the full version of the program will install.
Please go to this web page to download your installation file for your EndNote version:
https://support.clarivate.com/Endnote/s/article/EndNote-Installer-download?language=en_US