In order to cache an artifact from a remote Debian repository you will need to create a Remote Repository in Artifactory, providing the URL (e.g. 'http://archive.ubuntu.com'), and check the "Enable Debian Support" checkbox.
After creating this repository, you will need to add it to the sources.list file by running the following command:
sudo apt-add-repository http://<IP>:<Port number>/artifactory/repoName/
Once this is done, open your /etc/apt/sources.list file and add "#" sign to the first two lines (should be 'deb' and 'deb-src' lines) and remove the "#" sign from deb-src at the end of the file (the repository you just added).
For additional information about Debian signing on Artifactory please follow our Debian documentation for signing Debian packages. Once you define the GPG sign, signing the packages will be done each time you will run 'apt-get install <name package>' and the package will be cached into Artifactory.