Tap the Share button (square with an arrow) at the bottom.
Choose "Add to Home Screen".
Confirm with "Add". Otkucaj will appear as an app.
Click the install icon at the right hand end of the address bar (a monitor with a downward arrow).
If that icon is not there, open the browser menu (⋮ or ⋯): in Chrome "Cast, save and share" then "Install page as app", in Edge "Apps" then "Install this site as an app".
This route works even when the browser does not offer the installation itself.
In the browser menu (⋮ or ⋯) choose "Install app" or "Add to Home Screen". Firefox on the desktop cannot install web apps, use Chrome or Edge.
The app is already installed on this device.
The install window has already been opened on this page. The browser offers a new one only after a refresh, so refresh the page and click again.