When someone becomes the leader of the Catholic Church, they have a big party called a papal inauguration! It's like a special ceremony to celebrate and show everyone that they are the new leader.
During the papal inauguration, the new leader (who we call the Pope) wears special clothes and sits in a big chair called the throne of St. Peter. Lots of important people come to the ceremony, like other leaders of the Catholic Church, politicians, and even some regular people who want to be there to see it.
The Pope then gives a special speech to everyone there and talks about what he wants to do as the new leader. He also receives a special ring and a big hat called a miter to show that he is the Pope.
After the speeches and receiving the special items, the Pope gives a big blessing to everyone there and reminds them to be good and love each other. Then, there's usually a big parade to celebrate the new Pope, and everyone goes home happy and excited for the new leader of the Catholic Church!