To get the Postgres module working, all you need to do is to download it and put the postgres directory in the root of your project (ie, alongside sapphire, cms etc).
Then you need to edit the _config.php file (or _ss_environment.php file) in your project, and change the 'MySQLDatabase' value to 'PostgreSQLDatabase' and also change the username and password where appropriate.
That should be all you need to do. Run /dev/build on your project and all the tables should be created.
One final note though: you need to manually create the database, since the script can't create a non-existent database at the moment. Also, I highly recommend running 8.3.x, since T-Search (when we eventually get it running) needs to be part of the Postgres installation.
Thanks for giving the Postgres module a try, and let us know if you have any problems or code to contribute.