Instructions for GNU/Debian installation

Add the repository

Add one of these line to your /etc/apt/sources.list:
deb http://altern-deb.com/debian/  stable  main
Or
deb http://altern-deb.com/debian/  jessie  main
Or
deb http://altern-deb.com/debian/  altern-jessie  main
Or add the file altern-deb.com-jessie.list in /etc/apt/sources.list.d/.
sudo wget -q -O/etc/apt/sources.list.d/altern-deb.com-jessie.list https://altern-deb.com/debian/altern-deb.com-jessie.list
To add EFL Universe repository, add this line to your /etc/apt/sources.list:
deb http://altern-deb.com/debian/  eflu-jessie  main
Or add the file altern-deb.com-jessie.list in /etc/apt/sources.list.d/ and remove comments.

Install the GnuPG key

Install the signing key.
wget -q -O- https://altern-deb.com/debian/package-signing-key@altern-deb.com.key | apt-key add -
Or
sudo wget -q -O/etc/apt/trusted.gpg.d/altern-deb-jessie-stable.gpg https://altern-deb.com/debian/package-signing-key@altern-deb.com.gpg

HTTPS

If you want, you can use https instead of http.
  1. Install apt-transport-https package: sudo aptitude install apt-transport-https.
  2. Replace http:// by https:// in /etc/apt/sources.list.d/altern-deb.com-jessie.list.

Enjoy

Run aptitude update.
You should now be able to install the Altern-DEB packages you want with aptitude (or dselect, or apt-get as well...).