Does anyone know what the steps are and where do I start?
To turn your discourse forum into a google play button, “install” the website that you are on via Google Chrome. This will allow the site to be considered an app. This can only be done with compatible discourse forums.
However, it might be more complicated to turn things into apps for Google Play. Here is a blog post from another website that can help you get started:
there is already an app for every discourse forum in google play, it’s DiscourseHub
Here is a topic about adding the pwa to google play store. Discourse sites in Playstore