It's really easy!!
Step 1 - Head to hopsy.co.uk and log in:
Step 2 - Once successfully logged in, click the central icon - the box with the arrow.
Step 3 - Press 'Add to Home Screen'
Step 4 - Press 'Add'
Your iphone will add Hopsy to your home screen. It will look, and behave like an app. You will be able to use your iPhone's face recognition to log into your Hopsy account.
Please note, you need to 'Add to Home Screen' after logging in for face recognition to work.