You will go to GR and talk to them about your/the person in your groups need for it. if the CM finds you need a DAS they will scan your band and this is how you will use the DAS ( it used to be a card) you may use any band linked to your MDE )
someone said the bands are like ATM cards and this is true for 99.99999% of things at Disney ( so great way to think of it, and the only time something is on your band is when playing SOTMK)
MDE app shows that I have DAS and if there are any rides/times scheduled. In the past it has kept track of my selections however with Disney changing the experience to keep everything running smoothly, I don't know if this is still the case. We were down in April and I was able to access the info then.