To choose a firework type: Click on the options button (the three lined button.) It will show you the options. To make your very own firework, then click on the 'Firework: Custom' button, then you can put the dye it provides to you in the crafting grid! Once you are all done, then click 'Next'. Then answer the questions and it will tell you what to do from there. Then you are ready to watch your very own firework explode into the sky!!!