I can't remember exactly how PSE works in comparison with CS5, but you should be able to place the photo layer above the mask layer in the layers palette ... then, with one of the two layers selected, hold down the ALT key and place your cursor on the line between the two layers. Your cursor will change to a circle with an arrow ... now click the line between the two layers. The top layer will indent slightly in comparison to the lower layer. When you look at what happens on your layout you'll see that the photo layer clipped itself to the mask.
I hope I didn't confuse things ... the tutorials will be tremendously helpful because it will have screen shots usually ... and like I said, I'm not sure if the two apps work the same.
Good luck ... stick with it, cuz you'll get it eventually and be welcomed into the ranks of the addicted!