On Android using Chrome:
- Tap the menu button (⋮) at the top-right
- Choose "Install app" or "Add to Home screen"
- Tap "Install" to confirm
On iPhone using Safari:
- Tap the Share button (square with up-arrow)
- Scroll and choose "Add to Home Screen"
- Tap "Add" in the top-right corner
Open this site on your phone to install it as an app.