Rez the launcher on the ground and touch it. A menu will drop down allowing you to choose 6 altitudes, 4 spreads and 6 frequency for the fireworks, or turn launching on/off.
Choose "on_off" in dialog menu and it will launch 10 kinds of fireworks randomly.
You can also use voice commands on channel 66, as follows:
/66 on_off
Altitude: /66 height VALUE (default value is 20) The command will look like this: '/66 height 20'
Spread: /66 radius VALUE (default value is 0) The command will look like this: '/66 radius 0'
Frequency: /66 interval VALUE (default value is 5) The command will look like this: '/66 rate 5'