I've found myself telling people this anyways so may as well put it as in-app education:
Align the center of the BuzzCard over the NFC on your phone. If you don't know where the NFC sensor is, search " nfc sensor location" using your preferred search enginer
You'll probably have to fiddle a little bit to find the best spot
If you have a particularly thick case or your phone isn't recognizing BuzzCards (usually it should vibrate) at all, try removing your case
Sometimes someone forgets their BuzzCard or one just won't scan. You can use the Enter GTID manually button and type in their GTID to take their attendance.
I also like Capital One's mobile app simpler phrasing for this, which is essentially tap your card to the back of the phone, and if nothing happens, try again in a different spot.
I've found myself telling people this anyways so may as well put it as in-app education: