You should take some time to read the WordPress documentation and spend some time browsing your admin area to familiarize yourself with how WordPress works for you. Assuming that you have administrative privledges, log into your site: Dashboard > Settings > General and change the tag line – “just another word press site”- to whatever you like.
https://codex.www.ads-software.com/images/6/61/options-general.png
Some links to information that might be good reading and helpful.
Getting Started with WordPress
Working with WordPress
You can also find information about turning off comments site-wide, or on a per page/post basis in that information.