Choose a Paint > Select > Marquee   tool and drag over a region
            or choose Paint > Select > Magic Wand
  tool and drag over a region
            or choose Paint > Select > Magic Wand   and click a colored region.
  and click a colored region.
         
You can create a mask by selecting a rectangular, elliptical, polygonal or lasso region, or by selecting a consistently colored area of an image layer (magic wand). You can also add to or subtract from the selection.
When you select a region, the selected region is unmasked and all other regions are masked. You can then convert the selected region into a mask from the Canvas Layer Editor.
To select a rectangular, elliptical, polygonal, or lasso region
 (rectangle)
  (rectangle) (ellipse)
  (ellipse) (polyline)
  (polyline) (lasso)
  (lasso)The cursor becomes a knife.
For the Marquee (polyline) tool, you must click, drag, and release the mouse to create each segment. Double-click to close the selection.
 and open the Special
                           : Paint section.
  and open the Special
                           : Paint section.
                     To select a consistently colored area of an image layer
 .
 .
                  The cursor becomes a wand.
To select a different colored area, click it.
 again.
  again.
                     To convert the selection area to a mask
 to open the Canvas
                     Layer Editor.
  to open the Canvas
                     Layer Editor.
               A new mask layer called Marquee-# is created in the Editor. The selected region is unmasked and all other regions are masked.
This mask can be applied to any image layer(s), just like any regular mask.