Add repositories to the software package sources of ubuntu.
sudo add-apt-repository 'deb [path to source]'
sudo apt-key adv --recv-keys --keyserver keyserver.ubuntu.com FINGERPRINT_DES_SCHLÜSSELS
//for example spotify repo
sudo add-apt-repository 'deb http://repository.spotify.com/ stable non-free'
sudo apt-key adv --recv-keys --keyserver keyserver.ubuntu.com 94558F59