1. Open Photoshop. Open Image to work with layer masking basics.
2. Please understand the concept carefully. When you open the image the default layer is “Background” and it is locked. Masking option is not activated in this condition. You need to unlock the layer.
3. Double click and rename the layer to unlock it. If you don’t name it, it will take Layer 0 as a default name.
4. Using Elliptical Marquee tool, select the middle portion of an image.
5. Layer > Layer Mask > Reveal Selection.
Since the image has only one layer, it will be as follows before saving.
6. The layer will show the masking thumbnail.
7. The portion selected by the Elliptical Marquee tool is revealed and rest of the portion of the image is hidden by the mask. Here is the final image after saving it in Jpeg format.