For installing the new version of PostgreSQL 10 on Ubuntu Xenial 16.04 LTS :
sudo sh -c 'echo "deb http://apt.postgresql.org/pub/repos/apt/ xenial-pgdg main 10" > /etc/apt/sources.list.d/pgdg.list' sudo sh -c 'echo "deb http://apt.postgresql.org/pub/repos/apt/ xenial-pgdg-testing main 10" >> /etc/apt/sources.list.d/pgdg.list' sudo apt-get install wget ca-certificates wget --quiet -O - https://www.postgresql.org/media/keys/ACCC4CF8.asc | sudo apt-key add - sudo apt-get update sudo apt-get upgrade sudo apt-get install postgresql-10 pgadmin3
Source:
https://wiki.postgresql.org/wiki/Apt
https://wiki.postgresql.org/wiki/Apt/FAQ#I_want_to_try_the_beta_version_of_the_next_PostgreSQL_release