I came across the new packaging recently and to be helpful, I've put together a quick guide to using the code:
To begin, you'll need a smartphone with a QR scanner app installed (my phone came with it already installed so you might want to check your apps to see if you already have one before you go looking for one). If you're wondering what a QR code is, it's basically a 2-dimensional bar code.
You just go to the app page on your phone. Mine looks something like this (please ignore the three version of Angry Birds I have installed. I don't know what Asphalt 5 is; it came with the phone):
Once you click on the appropriate app, just center the code in the guides provided (it's pretty forgiving and very fast) and it'll prompt you to go to the site:
The site looks like this:
And voila! The Quarter Pounder with Cheese has a measly 2mg of Vitamin C (better pound that OJ!):
You can also use the site to get the nutritional information for your customized burger (say if you got it without onions or ketchup or whatnot):
You can find the new packaging from McDonald's at U.S. locations now and they're planning on rolling it out globally this year. That's about it. I hope it helps!