Can anyone tell me what exactly happens?
Having been through this about two dozen times...
You go in and give the lady your name. She checks the list and marks you down as having shown up.
You go over the table with a pitcher of OJ and pour yourself a cup.
You get called to the room and seat yourself where your place card is. Listen to any opening remarks. If you are taking the Christian oath, you do that. If you are taking the other oath, you do that.
You listen to GSTQ.
You get called up one at a time to receive your certificate.
You retire to the goodies table, possibly having a frame in which to put your certificate; possibly having something else.
You pour another cup of OJ.
Then you head to your local and put your card behind the bar.
Needless to say, I don't attend these any more. Now I only show up at the person's local.