Harvesting chillis is possibly the most rewarding part, after all this is what you grew your chilli plants for wasn't it?
Chillis can take 2 to 5 months to grow and ripen, it all depends on where you are and how much light and heat the plants are getting.
If your chilli plants are somewhere where there are no bugs or there is no wind you may wish to polenate the flowers by using your finger or a brush and gently transferring pollen from one flower to the next, try not to do this with different varieties of chilli otheriwise you will get some strange cross breads of chilli.
Chillis can be eaten at any stage, even immature, when they would be green, purple or cream. Eventually, most chillis will ripen to red or yellow. When you are ready to pick a chilli, gently pull and twist the chilli off the plant making sure you hold the main plant stem so that you don't snap it.
As the chillis ripen they become easier to remove from the plant. The more you pick them the more it encourages new growth and the more chillis you are likely to get.
Once picked if you aren't using them you can store them in the fridge, dry them or freeze them, more about this is mentioned in the questions section.