Add divs to separate the different sections of your page. Add, remove, rename and nest divs with a click of a button until you're happy with the layout.
Resize each div according to how you want it to appear on each device. Target common devices from wide screens to tablets, smartphones and even specific iPad and iPhone models.
Now that you're done, download your site layout and supporting css files that use media queries to arrange your pages according to the device they're viewed on.