Good news! EndNote X7 for the Mac now works with Microsoft Word 2016. When you open the desktop version of EndNote, it should tell you that that there is an update available, but you can also select Check for Updates in the EndNote X7 dropdown menu. EndNote Basic (the online only version) will also prompt you to install the new Cite While You Write plug-in for Word. Whether you are using the desktop or online version, you also need to have the latest version of Word 2016 (currently version 15.18) installed.
Once Word and EndNote are both updated, the EndNote Cite While You Write tools should appear as a tab in Word. The first time you launch Word 2016 after updating EndNote, you will be asked to “grant access” to an EndNote .plist file. Simply click Grant Access; you should not be asked this again.
More information about the update, including some troubleshooting in case the tools do not automatically appear in Word, can be found at http://endnote.com/kb/138936. More information about updating Word, with a more complete explanation about “granting access,” is at http://endnote.com/kb/138936.