Footer Settings

Go to Storefront -> My Themes -> Customize. (If your store is a new store, you may need to go to Channel Manager -> Themes -> Edit Theme)

In the Theme Editor -> go to Footer / Footer Settings

Sample Content of Power By:

All Rights Reserved. Powered By <a href='https://halothemes.net/'>Halothemes</a>.

When you are happy with your changes, don't forget click Save and Publish to repackage the edited theme.