I'm not sure if you're joking or if your experience has been very different from mine, but from the couple I've installed it was as simple as clicking a link (or menu) and then confirming.

> If only they could make the WebPage or WebApp installing on Home Screen as easy as pressing a link.

When you have the web page / web application open, press the action button, then select Add to Home Screen.

If you visit a Progressive Web App a couple of times, the browser may ask if you want to add it to the Home Screen. Works for me on Android at least.