You will need:
If you don't have an account, get a free one at http://github.com (it's not NECESSARY but we're going to use it for discussions and making the coursework better!)
Go to http://nodejs.org and follow the installation instructions, usually just clicking the big Install button.
After installing, test on your command prompt with: node -v
which should print out a version number.
This should have come with node. Test on your command prompt with: npm -v
which should print out a version number.
Go to http://nodeschool.io and find the workshop you're working on today. There should be installation instructions on each workshop's site or GitHub README file. Usually it consists of just npm install -g <workshop name>
If you don't have one, grab the Sublime Text trial at http://www.sublimetext.com/ which works on all (?) platforms