It's often a good idea to clip one of your bird's wings to prevent it from flying away. This is often better for your birds as they can be more vulnerable to predators if they were able to fly out of contained areas.

Blue = Coverts
Red = Secondaries
Green = Primaries
Wing clipping is fairly straightforward procedure which should be done a month or two after the birds moult. You will need to trim up to 6 cm off the primary feathers on one of their wings. When the feathers are clipped the bird should be able to still gain some altitude but will be off-balance and unable to fly completely. Wing clipping should not be too severe so that when the bird does attempt to fly and gain some altitude they don't completely collapse onto the floor and injure themselves.
You will need to get someone to help you especially if it is something new to you. Very gently get hold of your bird and clip the first 4 to 5 feathers as shown in this diagram. Be careful not to clip feathers other than the primary ones shown. If you see a feather that has a red shaft, it is because it is a blood feather and must not be cut. If you are in doubt you should consult your vet.
You will need to repeat this process each time the bird moults as new feathers will grow back. You should be able to see however where the previous cuts were made and repeat the same process.
Here is a video showing the process