I dont think you will find many videos online, its not the type of thing Marker would want widely available. People would be trying to adjust there own and make mistakes.
You could try to do the Marker Binding Certs. There will be a website specially made to help staff learn how to adjust the bindings. You would probably need to speak to a shop manager about getting on the program.
Better still just go into a shop which do Marker rentel bindings and get them to give you a quick lesson. All that is adjusted is the length between the heel and toe depending on boot size. Then its just a case of learning how to check forward pressure and how to work out the Din for a customer. A rental tech should be able to show you it pretty quickly, its not hard by any means, but would be by far the best way to learn.