Step 1:

Pick up 2 beads.

Pass back up the first bead added.

Pass back down the second bead added.

Step 2:

Pick up 1 bead and pass back through the bead you are exiting.

Pass through the bead you just added.

Repeat step 2

…

….

Repeat step 2 until you are satisfied with the length of your design.

And you are finished!