Photoshop Elements > Layers >
Masking >
Create a Layer Mask
Do the following.
1) Make sure the layer—where you want the mask—is active (highlighted).
Highlighted
2) Click the Add layer mask icon at the top of the layers stack.
The icon is the third one from the left.
The mask will appear in the layer.
Mask
By default, the mask is white.
Need a Black Mask?
If you need to change the mask from white to black, press Ctrl + i.
Black Mask
The layer becomes hidden due to the black mask.
Switching Between the Mask
And
The Photograph
When using the mask, make sure the mask is selected.
A mask that's selected has a blue border.
If it's not selected, click the mask thumbnail.
Mask Thumbnail Is Selected
When you're done using the mask, and want to do something with the photograph in that layer, click the photograph thumbnail.
Photograph Thumbnail Is Selected
More
If you haven't already, go to Layer Masks.