If you are logged in as the postgres account, you can create a new user by typing:
If, instead, you prefer to use sudo for each command without switching from your normal account, type:
sudo -u postgres createuser --interactive
The script will prompt you with some choices and, based on your responses, execute the correct Postgres commands to create a user to your specifications.
Enter name of role to add: danny Shall the new role be a superuser? (y/n) y