This layout is formatted in slim, which is a rails templating engine. To install google's recaptcha, after registering your site, and getting your api keys, simply add these following lines in your code where you need it in your views.
.g-recaptcha data-sitekey="your-site-key" data-callback="myCallback"
script src="https://www.google.com/recaptcha/api.js"
javascri...