I am unable to install a free app from the app store on my apple watch SE

How do I get my app to install on my apple watch SE? I find it through the app store on my watch, do the "get" thing and I got to the point where it says to double click the side button but nothing happens . The app is not listed on the Ruths Apple Watch list of apps on my I Phone 12 Pro Max, but I have the app installed on it. I would like to be able to control the volume on my Phonak hearing aids from my apple watch.