Custom link installation

Can you please elaborate a little bit more about your query? So that we will let you know back accordingly.

I would like to make a call to action button or link from where the pwa app for my website can be downloaded and installed.

This tutorial will help you to set up add to the home screen on click: https://pwa-for-wp.com/docs/article/how-to-add-to-home-on-element-click/

Maybe what I need is call to action premium service.