Choose a Paint > Select > Marquee tool and drag over a region or choose Paint > Select > Magic Wand 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
For the Marquee (polyline) tool, you must click, drag, and release the mouse to create each segment. Double-click to close the selection.
You can define your own hotkeys for the New, Add, and Subtract marquee operations. Choose Preferences > Interface > Hotkeys/Menus and open the Special : Paint section.
To select a consistently colored area of an image layer
If you want to set the Tolerance before selecting another area, without affecting the area you’ve already selected (for example, to add to the selection), click Accept or choose Paint > Select > Magic Wand again.
To convert the selection area to a mask
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.