In the guidelink you can see the next paragraph that I think answers your question:
Supported versions: We currently support Debian 6, Debian 8 and Ubuntu
14.04. However, the Debian 6 repository is compatible with Debian 7 and Ubuntu 12.04 as well.
So you just need to follow the steps for "Debian_6.0".
From the guide:
... So, for our public repository, you just need to add the following
lines with your favorite text editor (remember that you'll need
administrator access since this is a system file), replacing
with "Debian_6.0", "Debian_8.1" or "Ubuntu_14.04"
(removing quotation marks) depending on your target distribution ...