The easiest way to get loaf is if you have setuptools installed:
easy_install loaf
Without setuptools, it's still pretty easy. Download the loaf.tgz file from loaf's Cheeseshop page, untar it and run:
python setup.py install
If you'd like to help out, you can fork the project at http://github.com/whitmo/loaf and report any bugs at http://github.com/loaf/loaf/issues.
Start postgres:
$ bin/postgres -D /Users/whit/dev/loaf/var/pgdata
or:
$ bin/pg_ctl -D /Users/whit/dev/loaf/var/pgdata -l logfile start