Mark the spot
Bring the spacer as close to the hole as possible and use a pencil or marker to mark a spot where you will be drilling.
I used my Dremel with the supplied drill bit and hacked away a hole at the bottom end of the spacer. This will be done to two spacers.
The bit makes a hole that fits exactly to the size of the hole on the hard drive. Do this to the other spacer:
Flip the spacers around to the other end and measure two spots so you can make the other holes:
The other end
Take the Dremel and drill the same hole on the other end. To make it easier with less slipping, you may want to drive a pilot hole through the metal. These spacers are quite smooth.