For Debian 7.0 run the following as root:
echo 'deb http://download.opensuse.org/repositories/isv:/ownCloud:/desktop/Debian_7.0/ /' >> /etc/apt/sources.list.d/owncloud-client.list apt-get update apt-get install owncloud-client
You can add the repository key to apt. Keep in mind that the owner of the key may distribute updates,
packages and repositories that your system will trust (more information).
To add the key, run:
wget http://download.opensuse.org/repositories/isv:ownCloud:desktop/Debian_7.0/Release.key apt-key add - < Release.key