This is a horrible French braid (I know) and my first instructable! Follow me? :)
Step 1: Take Three Strands of Hair
Take three strands of hair from the top of your head (it's easier to learn on someone else). Make sure to have an elastic to secure your hair with.
Step 2: Braid Like Normal
Braid the three strands like normal for two cycles.
Step 3: Grab Hair From the Sides
Take the two strands of hair on the sides and add a little bit more hair to the strands from each side of your head.
Step 4: Repeat
Do the same thing until you get to the bottom of your head.
Step 5: Then
Once you get to the bottom of your head, braid the rest of your hair like normal.
Step 6: Secure
Put an elastic around the end of your braid. Then you're done! :)