Installing the Open Monitor Distribution (OMD) is actually pretty straight forward on Debian. Consol Labs provides a OMD repository from which the latest version of OMD can be installed, providing both a stable and testing branch.
First and foremost, you need to have a Debian/Ubuntu system running, and it needs to be connected to the internet.
In order to add the repository, you need to import the GPG security key in order to trust the repository: