A publisher or academic department may ask you to use a style that is not listed in the Word Style menu’s Select another style list. Where a file for the style you require is available from another source, you can can download it.
Up to date, style files available from EndNote.
OSCOLA styles for EndNote, Latek, Refworks and Zotero available to download.
IOE House Style file for EndNote
You should then be able to select your style by going back to Word and using the drop-down Style menu to Select another style. You should now be able to see your style in the list and to select it.
Please note, if you are using EndNote Online there is not an option to download citation styles.