First, create a design. I wouldn't try to use a lot of colors, just a few bright ones.
Now you tediously put seed beads on each head pin and trim and loop the excess. Make sure when you make the eye part that it's small enough so it won't slide off the eye pin.
On the eye pin, arrange the seed bead head pins, alternating head pin with seed bead (refer to photo if needed). I think it depends on the design if you're going to first put a beaded head pin or a seed bead on the eye pin, but I did beaded head pin first.
Trim and loop the eyepin to secure the "tassel." Attach to a chain, and you're done! Simple!