When scanning a dot using an iPhone, the sweet spot is right at the top, around the camera.
Dot cards can be scanned in two ways:
Tap it to the back of your phone or Open the camera app and scan the QR code
A link should pop up which will take you to the dot.Profile
dot cards can not be scanned while:
the flashlight is ON
the phone screen is OFF
their phone is in Airplane Mode
For all newer iPhones, released after the iPhone X, no extra steps are required.