The incense should only be light about 10 minutes before it is needed. Therefore there may be an adult in the sacristy preparing this for you. If not, the Priest or the Deacon will indicate when you need to prepare the incense.
There are charcoal tablets that are placed in the boat. When it is time, the altar server brings the boat and the Thurible to the Priest or Deacon. They will spoon the incense ashes from the boat to the Thurible.
When not in use the Thurible has its own stand that is located by the credence table.