Q re installing Pg on OS X?

I'm trying to install PostgreSQL on my Mac laptop.
I used MacPorts for the first stage of the installation. I did the
following:

% sudo port install postresql82 +perl +python

This took quite a while to complete, but it ran without a hitch.

From that point on I followed the instructions given in

http://developer.apple.com/internet/opensource/postgres.html

although I had to make significant modifications to their procedure (for one
thing, they use Fink to install the software whereas I used MacPorts; and
they refer to v. 7.4.1 as the most recent version of PostgreSQL, so the
instructions are somewhat old).

Per these instructions, I created a postgres user, logged in as it, updated
my PATH, started the server manually, and created a database with

% createdb test

After this point I am able to log in as the postgres user using "psql test".

But I can't log in as any othe user. I get the errors like this one:

FATAL: role "root" does not exist

The instructions I'm following have nothing to say about "roles". (I figure
this must be a post-7.4.2 feature.)

Can someone point to more up-to-date installation instructions for OS X?

Thanks!

kj