1) Include the image name in the .csv file for upload.

The image's name, is the name you gave it when you originally added the images to the gallery.

Example .csv file content with Image Names:

Ann Smith, smith@mycompany.com, Image1.jpg
Alex Anderson, alex@mycompany.com, Image2.jpg
John Jones, john@mycompany.com, Image3.jpg

2) Assign your image column to the appropriate image group.

In this case, the Image Group these images are associated with is "Dogs."

3) After the upload is complete, the appropriate image will be associated with each contact.