It is a little more difficult rear wheel change because of the horizontal dropouts. My best advice is to stand directly behind the bike, with your thumbs on the top of the dropouts and your right hand on the rear derailleur. It also helps if you completely remove the quick release skewer but this is not required.
Pull the body of the derailleur towards you as far as you can, that will move the top jockey wheel back, and give you more room to wiggle the rear wheel off.
Another option is to pull the chain back (from the top) with your fingers, and then slide the wheel out of the dropouts. This way is easy, but involves getting some grease on your hands from the chain.
Horizontal dropout provide a major advantage in aerodynamics, as the wheel is hidden perfectly behind the seat tube, but they can be a little tricky to work with.