All you need: Yarn Needle or Tape Pencil Cup from Dollar Store I didn't have a needle that would be big enough for the yarn and also small enough to thread through the holes in the cup, so I twisted the end of the yarn and taped it up tightly. That's what I used as a "needle" and it worked great. Like so:
Then just thread the yarn through in any pattern you like. I did a very simple up-and-down pattern. Adds a little extra color and zip to a plain pencil cup for very little money and just a little time!