On iPhone (using Safari browser)
You will see the app in the browser and a popup to Install the app and 'ADD TO HOME SCREEN' will appear at the bottom of the screen.
When you click the blue "ADD TO HOME SCREEN" button you will then see instructions for how to add to the home screen on iOS
Tap the relevant icon then press the Add to Home Screen icon (note you may need to scroll to see the Icon).
Next click 'Add to Home Screen'