Ah, are you hosting with Webflow? Then might not be possible yet - see - Add code in htaccess
If you have access to a host you could try exporting your code and copy it over. Then add the IE code above to a .htaccess file and test. At least you would know if it works for your site. There are variations on the problem, i.e., <IE11 browser, those using/not using compatibility mode etc. So might take a little trial and error and some Google research.
Good luck!