: An alpha channel is automatically added into the Channel Dialog as soon as you add a second layer to your image. It represents the transparency of the image. If your image has only one layer, this background layer has no Alpha channel. In this case, you can Add an Alpha channel with this command.
You can access this command from the image menubar through
→ → .In addition, at the Layer Dialog, you can access it through of its context pop-up menu.