Wow, amazing how healthy your plants looks. The container seems to be a bit small already for the size of your plant.
A few tips about pruning.
First, prune at the right time. This is usually early spring, just before growth season starts.
Second, try to figure out what the desired height of your plant is going to be. Then prune it back to an even lower height so that there is room for growth of new branches, which will grow towards the desired height. Also keep in mind to put it in a large(r) enough container, which can support the eventual height.
Last point, a general rule of thumb with pruning is to never prune off more than 1/3 of the plant. Some plants may not survive more.