First, take your yarn. You'll need about 7 strands, depending on what result you'd like and the width of your yarn.
Make a knot. Don't make it too tight, this knot is gonna be removed at the end
Divide the strands in two groups: one with three and one with four strands.
Now you can start braiding.
Start with the group that has four strands. Take one of them and bring it to the other group. Now, take a strand from the group that NOW has four strands and bring it to the other side. Repeat this until you like the length to be your bracelet. Make a knot after your begginning knot, on the first braided part. Knot it really tight. Cut the remaining strands, your bracelet is finished!