Same header and footer in admin across all sites in network

Hi WPMU!

I want to display the main site header and footer in the admin of all of our subsites, but I don’t know how it can be done.

I have read a post on stack exchange: http://wordpress.stackexchange.com/questions/231790/same-header-footer-in-admin-across-all-network-sites-in-multisite and the user says he made it work, but I can’t find out how to create it.

Can you help me?