Packages for Ubuntu 16 (Xenial), Ubuntu 14 (Trusty), and Ubuntu 12 (Precise) are available in the SaltStack repository.
Instructions are at https://repo.saltstack.com/#ubuntu.
Install the Salt master, minion or other packages from the repository with the apt-get command. These examples each install one of Salt components, but more than one package name may be given at a time:
apt-get install salt-api
apt-get install salt-cloud
apt-get install salt-master
apt-get install salt-minion
apt-get install salt-ssh
apt-get install salt-syndic