cURL is used to fetch data from the Internet or Local Network and is required

Hi,

Could you please read this article - Xibo CMS Installation manual
Then after you will have CMS installed, this guide will help you with other settings - Xibo CMS Post Installation Guide

Curl is a php extension used to exactly what you said. You might be missing CA root certificates or you might have some kind of problem with your php installation. For more details please have a look here - Curl, CA root certificates.