I think she's referring to editing programs to make the screenie pack cover art?
If so, photoshop and gimp are the most commonly used since they are generally user-friendly with layers and editing. Gimp is free and easy to get, and photoshop usually must be bought. There are free versions out there though, but nothing I can link. While GIMP is usually considered lower quality, you can generally do anything on Gimp that you can do on photoshop. It all boils down to how much practice and research you do yourself to improve and play with how your display packs look.