add a new repository to easily install a recent version of Postgres

sudo sh -c "echo 'deb http://apt.postgresql.org/pub/repos/apt/ xenial-pgdg main' > /etc/apt/sources.list.d/pgdg.list"
wget --quiet -O - http://apt.postgresql.org/pub/repos/apt/ACCC4CF8.asc | sudo apt-key add -
sudo apt-get update
sudo apt-get install postgresql-common
sudo apt-get install postgresql-9.5 libpq-dev

You will now have a user named postgres with no password

sudo -u postgres psql       # enter the psql environment as the user postgres
\q                          # quit psql environment

create a user with permission to create databases

sudo -u postgres createuser roycan -s

# If you would like to set a password for the user, you can do the following
sudo -u postgres psql
postgres=# \password roycan