Can you specify the library you're trying to work with if there are multiple for this character? Providing an answer to your question is difficult if you don't state the exact library/ies you are using.
Edit: Okay... I can see that the hakuapoid_kyo_eb.zip is made entirely of end breaths and intended to be used with hakuapoid_ren_ver2.0_kyo.zip
Just place the _endbreath folder inside the main folder of the library. To set up ending breaths, Alt+T then Alt+U then Alt+S. This will open the Suffix Broker. Add the following: 息 with a single space in front of it. Press the plus button. This makes a suffix you can add to the end of vowels with the following notations: a 息, i 息, u 息, e 息, o 息, n 息
You will have to edit the note you want to change to romaji for the breath to work.

