Cacher is the code snippet organizer for pro developers

11.28.16 - theme developer (Bloom Blog Shop)

You can add the code snippets to the functions.php from Genesis, or what may be easier is to download this plugin:
https://wordpress.org/plugins/genesis-simple-edits/
Then you can go to Genesis > Simple Edits and edit the footer credits there!

I used Simple Edits and it's fine, but I also will try out the other methods.

12.7.16 Matt Hind - StudioPress Forum
I've just been struggling with this and found the solution to be to add the 'customize entire footer text' code snippet in to the genesis-changes.php file NOT the functions.php file.