In your administration site, you'll want to see the "Customization" and "Integration" sections. The customization will allow you to visually customize the site to integrate seamlessly with your existing site. The integration section has widget builders and API which will allow you to seamlessly integrate Q&A calls to action and functionality into pages of your existing site. Both of these accomplish a seamless integration. You'll of course want to add a link to your Q&A environment within your current site as well, so its easily available in the navigation of your site.