Outer Glow is a Photoshop effect that can be used to add an extra level of brightness to your photos. To apply Outer Glow, first open the photo you want to add Outer Glow to and select the Brightness slider at the bottom of the dialog box. Next, click on the Add button and select Outer Glow from the resulting list. Once you have added Outer Glow, click on the OK button to close the photo editor and return to your original photo.