Depending on the clearance around the bottom of the skimmer cup and body of the skimmer, you can look to put in a straight or 90 degree fitting. Also dealing with clearance, either a 1/8" or 1/4" fitting. If using a 90 degree, make sure you will be able to turn it without hitting the skimmer. The fitting is a threaded barb, fine threads on the cup end and a saw-tooth looking, slide on fitting for the drain hose. Drill a hole in the bottom of the cup, as close to the outer edge as possible. Once again, clearance. If drilling the bottom isn't going to work, drill into the outer wall of the cup, as close to the bottom as possible. If you have the tools to 'tap' threads into the hole, ok. If not, drill the hole big enough to allow the fitting to slip in...snugly. Glue or silicon the fitting in. Slide the hose on the barb, and you're all set.

HTH