What do I have to do to get the Modernizr module to work in Drupal? I would like to use modernizr in drupal to take adcvantage of css media queries, box-shadow and border-radius. I have followed the installation instructions perfectly. I have installed the Drupal Modernizer module and created and properly placed my customized Modernizer build to include support for these three features. Does modernizr just pick up my already existing media queries and css3 styles automatically or do I have to do something else?
Modernizer detects feature support in browsers and adds css classes to the HTML element based on those features.  You use those css classes to target newer features to browsers that support them.  While it will add HTML5 support to older browsers via the HTML5Shiv, it will not add CSS3 support.

To add support for CSS3 features in older browsers, you'll need to add a polyfill  Modernizer has a method called Modernizr.load() that lets you load the polyfill only when you need it.