This is fun part! First, start by taking the outer most stand on the left and weaving OVER-UNDER-OVER. Next, weave the outer most strand on the right UNDER-OVER-UNDER, and across the first outside strand. And REPEAT!
As your braid gets going you want to tighten strands so they are even.
You should end up with a braid about 1 3/4 inches wide and 14 1/2 inches long. (The measurements will vary depending on how tight your braid is.)