All you do is gather only the top part of your hair and start fishtail braiding. Fishtail braiding is where you part your hair in 2 equal pieces and take a tiny section of hair from 1 side and bring it to the other side,then take a tiny piece of hair from that side and cross it over to the other side. Keep repeating that and pretty soon you will have completed the braid. If this doesn't make since to you,you can check out YouTube for some great tutorials.
Happy Braiding! ;-)