Hays,
Elements has Layer Masks, but you have to go "around the barn" to use them.
Create an Adjustment Layer below the layer you wish to mask. Don’t make any adjustment, just accept it as default. This gives you a layer with a mask which you can use.
Group your original layer with the new Adjustment layer. Your original layer should become invisible, because it is now masked by the Adjustment layer’s mask.
In the Layers palette, click the right-hand icon (layer mask) of the new adjustment layer. Paint with white to show your original layer, or fill with white to show the whole thing, then paint with black to mask. Gray values painted will show correspondingly varied opacity.
Or, you can download one of the free add-ins for Elements which gives you the ability to add a true Layer Mask to any layer. Go to
http://home.cogeco.ca/~challenge/index.html and click "Links" at the bottom of the lefthand column. On the Links page, you’ll find links to Paul Shipley’s tools, and the Hidden Power tools. Both are excellent and will do the job, and more. (I use the Hidden Power tools, because I have also purchased Richard Lynch’s book, which comes with the FULL set of Hidden Power tools, and everything works seamlessly — but, in a former incarnation, I used the Shipley add-ins with no trouble)
Write back if you need more.
Byron