We create a layer by clicking on the Layer tab above the image. In this case, select White Fill
type. The new layer will appear as a white image, and be represented as a white rectangle labeled
'New Layer' in the Layers panel to the right. It is on top of the original image, which has
temporarily disappeared. Click on the eye next to the New Layer in the Layers panel, the new white
layer will no longer be visible (although it is still there) and the original image will reappear.
Click again, the eye comes back and you see the white layer. No eye, no see; the next image shows
this. Poke that eye to hide the white layer.