I am attempting to install CQRLOG on a PC running Ubuntu MATE 16.04. It all goes well till the final step, where it says that a media change is required. Specific text is as follows:

"Need to get 0 B/32.6 MB of archives.
After this operation, 203 MB of additional disk space will be used.
Do you want to continue? [Y/n] Y
Media change: please insert the disc labeled
'Ubuntu-MATE 16.04.2 LTS _Xenial Xerus_ - Release i386 (20170215)'
in the drive '/cdrom/' and press [Enter]"

However, my Ubuntu MATE was installed from an iso image on a USB Drive, so it is not clear how to satisfy this request. The process is stuck at this point and I was not able to kill the process without restarting the PC. Please advise on how to get around this. Thanks for your assistance.