Take a look at the postgresql section here:
Covers the basics on editing your 2 config files. After you make config changes, you'll need to re-start the server.
If you don't change the "listen" directive in postgresql.conf your other changes won't matter it'll only take directives from the local machine.
Please visit: http://www.xtuple.org/phpBB3/viewtopic.php?f=&t=3525&p=0 for the changed document