You need to check out the snippets on the themesandco.com site.
To change the icons next to the titles etc, see this snippet: http://www.themesandco.com/snippet/removing-page-icon-left-page-title/
To alter the footer credits, see this snippet: http://www.themesandco.com/snippet/altering-adding-footer-credits/
See also the articles on how to set up a child theme and How to customize Customizr.
Come back if you have more problems.
....with thanks to Google translate! :-)