Adding the apt repository

If you are using Ubuntu, make sure the universe repositories are enabled

The repository is added like ever other apt repository: Create /etc/apt/sources.list.d/jitsi-stable.list and enter the following line in it:

deb https://download.jitsi.org stable/

Afterwards add the GPG key with

wget -qO -  https://download.jitsi.org/jitsi-key.gpg.key | sudo apt-key add -

and update the repository with

sudo apt-get update