Photoshop is a powerful image editor that can be used to fill in selections, create logos, and more. There are many ways to fill in selections in Photoshop, but the most common way is to use the selection tool. To select a part of your image, click on the selection tool and drag it around the image. You can also use the arrow keys to move the selection around. When you have a good selection, press Ctrl+C (Windows) or Cmd+V (Mac) to copy it and then paste it into another document.