It's time to make some honey! Supering is when you add another box to you hive. When supering for honey there are a few tricks that can actually increase the amount of honey they produce.
Once your hive is 70-90% full it is time to add a box. You can tell how full a hive is by how many frames they are working.
If you have not yet added a super, place the super on the very top of the hive. If the super is full of foundation (rather than drawn comb) you can feed them once or twice to help them produce wax. You will want to stop feeding once they have drawn wax out on 3-4 frames. Do feed them if the super is full of comb. The bees will store the sugar syrup in the comb and adulterate the honey.
When adding the first super, if it is foundation, you will want to wait before you put a queen excluder on. Bees do not like to produce foundation through a queen excluder. Wait till they have drawn out 3-4 frames with wax before using a queen excluder. The queen excluder is inserted between the brood chamber and honey super. It keeps the queen from laying brood in your honey.