How to remove / change the Powered by text?

I follow the guide here https://catchthemes.com/theme-instructions/clean-box-pro/ How to add Footer Left Content and Footer Right Content (Footer Copyright Information)? Go to “Appearance => Customize => Theme Options => Footer Editor Options” Under Footer Left Content you can add html or plain text Then under Footer Right Content you can add further html or plain text for Right section Finally, click on “Save & Publish” --- but it didnt seem to work? please help.