It's how Leica's work. It's a bit strange, but as unclemack stated, easy once you get used to it (though I wish I had a third hand for the base). Take the base off, pull the leader out a bit, put the film and leader in through the bottom of the camera. You just make sure the end of the leader reaches into the take up spool. Then you flip the back up, and make sure the film is pushed up far enough into the camera, so it's centered on the rails. You can also see that the little teeth on the take up side are engaged in the sprocket holes. Close the back, put the bottom on, and fire off two shots.
Some people recommend folding over the tip of the leader and/or winding a frame on before you close up the back, but I've never needed too. When you shoot off your first blank shot or two, just look for the rewind knob to turn. That's good practice, but again, I've never misloaded a roll.
It really is easier than it sounds. I'm sure there are videos/pics of it on the web.