If you don't already have it: gem install rails
.
Download the Postgres app.
OR: Use Homebrew to install Postgres:
From your terminal, run:
brew update
brew install postgres
ln -sfv /usr/local/opt/postgresql/*.plist ~/Library/LaunchAgents
launchctl load ~/Library/LaunchAgents/homebrew.mxcl.postgresql.plist
These last 2 lines will set up a special Daemon init file so that your operating system will start postgres automatically whenever you log in.
All information taken from the Turing School Module 2 Prep Work.