Install
First install 'crawl' and 'capture'
npm install -g crawl
npm install -g capture
Note: 'capture' requires PhantomJS. I generaly install using homebrew on a Mac.
Crawl Site
You first need to crawl your site and produce a sitemap of every page found within the domain. Use 'crawl' to do this:
crawl -j http://your-site.com > sitemap.json
Capture Screenshots
Next you can capture screenshots using 'capture'
capture -s sitemap.json -o ./output-directory