PostGRE SQL installation issues

hi all
I use FreeBSD 4.10. I downloaded the packages for PostGRE SQL (7.4.2), and installed the packages.
I also happened to see the messages "created user postgres" & "created group postgres".
Then executed the initdb and started the postgres server.
Now when I do a ps, postgres shows up.

How do I go about creating a sample database (does a preconfigured sample DB exist)?
regardless of whether I issue createdb or createuser, I get the error: user xxx not found.

Thanks for any help

Tk

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