In order to have EndNote show the references in reverse chronological order, you may have to follow the steps listed below:
In the dialog that appears, enter a new name for this modified style, and then click Save.
Please note that any changes that you make to the style in EndNote will not be updated automatically in your Word document. You will have to manually change to the modified style within your Word document.
Follow the below link for more information about changing the output style within a Word document: