apt - How to use a .iso image as a CD-ROM Repository?

I have all images of Debian, Ubuntu and Ubuntustudio as .iso. How can I use them as repository to install my desired packages with sudo apt-get install package-name?

I easily mount the .iso file with Archive Mounter, but when adding CD-ROM in Software Sources it says Please Insert CD-ROM.

How should I do this without burning them to disk?