Follow these steps to install Spur on your phone
Open Spur on the Safari or Chrome browser & login via this link
While viewing the website, tap the menu bar on Safari or three dots menu on Chrome.
Scroll down the list of options, then tap "Add to Home Screen".
If you don’t see Add to Home Screen on Safari, you can add it. Scroll down to the bottom of the list, tap Edit Actions, then tap ➕ Add to Home Screen.
Next steps would be to enable notifications, for that please follow this guide.