First create a postgres user and database with your username. When using psql, you will open a database with your username as default, so its easier to create the table with your username at the start.
~$ sudo su postgres -c createuser yourusernameNow connect to your postgres database and alter the password the user that has just been created.
~$ sudo su postgres -c createdb yourusername
~$ sudo su postgres -c psql yourusernameDon't forget the terminating ; in the SQL call. I found these helpful hints in the postgres manual for version 8.0:
=# ALTER USER yourusername WITH PASSWORD 'yourpassword';