Erin's instructions for Retreat guest boarding in Miami are accurate. My wife and I have sailed from Miami as Retreat guests on both Summit and Silhouette a number of times since sailing has restarted. Silhouette will be using terminal "G".
The “Priority Curbside Drop Off” will be at the far end of the baggage drop off area. The banner is a tall sign but is some times hard to find because of all the people. At this drop off area there is a small podium and sign for Retreat guests where staff will great you and escort you as Erin described. If there is no one at the podium don't panic... they are taking care of earlier arrivals and will return shortly and take good care of you.
Embarkation is rather hectic as you probably know, take your time, your guide will get you through all the check in steps. Enjoy the Silhouette and have a great cruise