HowtoMatrix

Instead of inserting (or even burning) multiple CDs to install software in debian you can just use the downloaded ISOs.

This method assumes you are going to keep the ISOs and folders available, the ISOs will be mounted at boot time automatically and you will be able to install software from them at any time.

Be sure to replace any instance of my-user-name with your username.

First create a folder in /home/my-user-name/ called isos

Now store all your downloaded isos in /home/my-user-name/isos/ and the isos are named debian1.iso debian2.iso debian3.iso

Read more at Debian Admin