One of the many features of the Happy Home Paradise DLC for Animal Crossing New Horizons is amiibo support. The main game features amiibo support that allows you to bring in villagers to stay at your campsite. Needless to say, the amiibo support for Happy Home Paradise is different. Instead, you get to design vacation homes for the villagers you bring in.
Before you can do anything with amiibos in the DLC, you will first need to access it. As soon as you start up the game, you will get a call from Tom Nook requesting that you go to the airport. One trip to the airport later and you will be meeting Lottie. She invites you to come work for her at this new chain of islands where you will design vacation homes for villagers.
After completing enough projects, Lottie will give you a promotion. Shortly after your promotion, she will introduce you to the amiibo reader. The amiibo reader sits on her desk in the main office building. Whenever you want to bring in one of your amiibo villagers, interact with the amiibo reader and scan the amiibo figure or card.
Most of the characters brought to the island this way will have a simple design request. There are, however, VIP members that can be brought in. These characters require a little more work and you will need to decorate more than their house to satisfy them.