How do I make my Image go full screen width?

How do I make my Image go full screen width?

How do I make my Image go full screen width when viewing on a mobile,
noting that it's not meant to be fullwidth on a desktop. An example to
make it even more clear. Microsoft's home page has a slider that is not
fullwidth, but resize the browser and it goes fullwidth without any
padding. I can't figure out what I need to do in my css to make that
happen. I know I have to add something in media query, and I've tried, but
haven't succeeded. Link to my site.