Open a crafting table
Place 1 paper and 1 gunpowder to make 3 fireworks rockets
Place 1 paper and 2 gunpowder to make 3 fireworks rockets with longer flight duration
Place 1 paper and 3 gunpowder to make 3 fireworks rockets with the longest flight duration
Use rockets with an elytra to boost flight
Add firework stars if you want explosion effects
Combine paper, gunpowder, and firework stars in the crafting table to customize fireworks rockets