Replace images in your gallery from Gallery Settings.

To change an image in a gallery:

1. Click the gallery to select it.
2. From Gallery Settings, click Organize Images.

3. From the left of the Organize Images window, click an image.
4. From the right of the Organize Images window, under Image, click Change.
5. From the Image Gallery, click an image or upload an image. Click Change Image.

6. From Organize Images, click OK.

Your image changes in your gallery.

For more information on Galleries, click here.