Phonetic Guide / ruby text MSW for Mac 2016

Question

In the new version of Word for Mac, when using the phonetic guide, the program separates the word into letters. It's possible to edit the boxes, but if you do, the 'OK' button becomes disabled. I tried to add Japanese katakana above an English word to help young learners learn new words. This wasn't a problem in MSW for Mac 2010. I select the word as with the 2010 version but am only allowed to add phonetics above individual letters. I've included some screen shots to hopefully better illustrate this problem, the first of which will be the 2010 version that allows phonetic insertions above selected text. The following screen shots are of 2016 version. The last one shows what I want to accomplish but cannot because the 'OK' button is no longer available.  Thank you!