A feature to disable Powered by icon will be included in RVsitebuilder CMS soon. Now you can remove it manually by domain name with the following guide:

1. Go to cPanel -> File Manager -> /home// -> rvsitebuildercms -> Domain Name folder -> .env

/home//rvsitebuildercms//.env 

Where to find .env file

2. Go to cPanel -> phpMyadmin.

At the database you got from number 1, table "core_footer.

Edit column content_view and content_edit

4.Find "Powered by RVsitebuilder" and remove it.

5. If you update the website content or change footer of the website, you have to do this steps again.