• Click on the image, and from the Selection menu,
  select Open in.
  
  
• Select the application you want to use. This application will open, and the image you selected will be shown.

Note:


(When you first use PhotoGrid, no applications will be visible except the one that created the image in the first place.)

You can choose another application temporarily by selecting Choose App to open... from the Selection menu. Then use the standard Mac dialog to navigate to the application you want.