Before you take any steps please back up your files and database. The plugin works only with default CMS pattern. If you manually changed CMS patterns, the plugin might not help you.
This tutorial guides you through the CDN integration of Typo3 with the smile_cdn extension. We used Typo3 6.2 LTS and smile_cdn version 2.1.0 in the following example.
Login to the Typo3 backend.
Navigate to Extension Manager and install the extension smile_cdn.
Configure the smile_cdn extension by defining the CNAME (without http://) that you specified in the G-CORE control panel and the desired filters to offload your assets. Ensure that your CNAME record has been configured in a proper way before using it for integration.
Click Flush the Frontend Caches in the Typo3 backend.
Integration has been completed! We highly recommend you to check the HTML code of your web page to ensure that URLs have been rewritten properly from your original ones to CNAME from the control panel.
To do that press F12 or open Developers Tools in your browser, choose the Network tab and refresh the page. All static files should have your CNAME in URLs.