Start by brushing out your hair, then putting it in a (very loose) side pony tail. You don't have to put a hair tie at the top, but i find it easier like that.
Split your pony tail into 2 even halves.
Take a SMALL strand of hair from one half of the pony tail. (It will look better if you take the hair from the hair from the back of the pony tail)
Cross the small strand you picked up, over to the other half. (It wont be very noticeable at first).
Now repeat step 4 with the other half, take a small stand and add it to the other half.
Keep repeating steps 4 and 5 until you get to the bottom of your hair, it should look like the picture.
If you used a hair tie at the top, then gently pull it to the bottom of the braid, and wrap it around tight. This will make it look messier, which i prefer. If you didn't use a hair tie, then just out on at the bottom of the braid now.
The finished product should look something like this!:)