Create new postgres super user

gistfile1.txt

Run this 
        "sudo -u postgres psql" 
in your terminal to get into postgres

postgres=#

Run "CREATE USER new_username;"

Note: Replace new_username with the user you want to create,

postgres=# CREATE USER new_username;
CREATE ROLE

Since you want that user to be able to create a DB, you need to alter the role to superuser

postgres=# ALTER USER new_username SUPERUSER CREATEDB;
ALTER ROLE

To confirm, everything was successful, 

postgres=# \du
                             List of roles
 Role name |                   Attributes                   | Member of 
-----------+------------------------------------------------+-----------
 new_username     | Superuser, Create DB                           | {}
 postgres         | Superuser, Create role, Create DB, Replication | {}
 root             | Superuser, Create role, Create DB              | {}
 
postgres=#