Lynn, the variables that you need to change to straighten out the database usage information are also in the configuration.php file:
$mosConfig_host = 'your databae host';
$mosConfig_user = 'your db userr';
$mosConfig_password = 'your db password';
$mosConfig_db = 'your database name';
$mosConfig_dbprefix = 'your table prefix';
Just edit those to the values for your DreamHost Joomla! database, and you should be good to go.
Later Joomla! versions allow all of these except $mosConfig_password to be set interactively from the Joomla! administrative back-end (Site -> Global Configuration -> Database), so you can also set them from within Joomla! by just logging into the administrator, or you can just edit them directly in the configuration file. .