This is based off the work done by lorint. We've already done the work to convert the csv's to be compatible with postgres. If you would like the original files, head over to Adventure Works 2014 OLTP download page. The download includes a script for loading the data into MSSQL Server.
First, make sure you have postgres installed. You can do this by typing psql in terminal.
If nothing comes up, install postgres using brew install postgres. This will install and initialize a postgres database.
Head over to https://www.postgresql.org/download/windows/ and follow the instructions.
Once you have confirmed your postgres install, run the following two lines:
psql -c "CREATE DATABASE \"Adventureworks\";"
psql -d Adventureworks < install.sql
You're all set!