Complex sentence: Upon arriving at the stable where Jesus was born, the Magi worshipped him and opened their gifts, with Melchior giving the gift of gold to signify Jesus' kingship over the world.
Split into simpler sentences: Upon arriving at the stable where Jesus was born, the Magi worshipped him and opened their gifts with Melchior giving the gift of gold. The gift of gold was given to signify Jesus' kingship over the world.