To replace a single image in a project:

1. Click Projects on the main menu at the top of the page.
   
   
2. Select the project you are working with:
   
   
   
3. Click on the Edit button near the right side of the page:
   
   
   
4. Select Photos on the progress bar:
   
   
   
5. Click on the replace button under the thumbnail of the image to be replaced:
   
   
   
6. Choose the location that contains the image you want to use (e.g Album Photos):
   
   
   
7. Click the check mark under the image you want to use, then click the Add Selected button:
   
   
   
8. Crop the new image if needed, as in the example below:
   
   
   
9. Click the Save and Continue button to save your changes: