When you enter at the homepage it will apepear a message at the bottom which will invite you to install de app. If it doesn't appear, you can click the option "Add to Home screen" in the Chrome menu
Clic share at the browser options and select the Add option at the initial screen
Now Chrome doesn't have an option to add to home screen. You can add the app manually at the home page.
Clic the options menu at the browser and select the option "Install Gran Teatre del Liceu"