I have been watching the tutorial "How to make a website with Dotnetnuke" and in part 6 video 4 Lee shows how to use a skin.xml file he created to change the menu from Horizontal to vertical. Its all very clear except where to find the xml file. Can you tell me how I can obtain it.

Hello,

Have you downloaded the code that is included with the videos on this page:
How to create a skin for DotNetNuke

Inside the Vortex skin is a skin.xml file that you can use. The tutorial based its changes on the DNN-Blue skin and you can also use the skin.xml file as a starting point from the DNN-Blue skin, example code of this is also included on that tutorial page, thanks,

Thanks!  It was there.