Step 1: Required Parts and Tools.
Simply plug in the hot glue gun and switch on, wait until the glue is hot enough to flow and drop a small blob onto the pompom. I tried to open the pompom up so the glue would be as close to the centre of the pompom as possible. Before the glue dries, put the small button Lego part on the glue. Opening the pompom up before glueing ensures the Lego part is as hidden as possible when attached to the character.
Step 2: Finished Item.
My character doesn't seem very impressed with the wig, maybe its the colour.