We can print on the front, back and inside of cards however you need to upload these in one image file. It is not currently possible to add multiple images to the card template within the prodigi dashboard.
You can download templates from individual product pages on the website or from the file requirements if browsing products within the dashboard.
The downloadable PSD templates can be opened in Photoshop as well as other image editors like Gimp or Lightroom.
We have this video which shows how to use templates with photoshop