How to install app on smartwatch

I have been using BackCountry Navigator Pro for many years.  I recently got a WearOS watch.  I cannot see an option to install the app onto my watch - the play store says it is not compatible with a smartwatch so cannot install it that way.  The article on the web page says the app will be installed on the watch when it is installed on the phone.  The app has been installed on the phone since I upgraded a year ago.