Clamp spool in a vice or hold on tightly and use drill and large drill bit to hollow out one side of the spool. The larger drill bit the better, but not so large as to drill out the side. Drill down about 2/3 of the way down to create a hole large enough to fit the earbuds into. Then use the smaller drill bit to widen out the hole on the other side in order to fit the plug of your cord through. This smaller hole needs to be large enough to fit the cord and the plug in at the same time.