You'll get instructions onboard (via a letter in your cabin). You'll be told to meet somewhere at a certain time in the morning, hang out for a bit while everyone else disembarks, then be led into the terminal (briefly) to go through customs, get new sea pass cards, then be led back onto the ship. It's business as usual after that. You have to do muster again like any other cruise.
Looking forward to a few Utopia B2B's myself but not for a while.