The Preloader Widget is exceedingly simple to use. Just create an array with the paths to the images you want preloaded and register listeners for load and timeout events...

var myImagePaths = new Array();
myImagaPaths[0] = "image1.gif";
myImagaPaths[1] = "image2.gif";
.
.
.

var myPreloader = new ImagePreloader(myImagePaths, <timeout>);
var listener = new Object();
listener.onImageLoad = function(path, numLoaded, totalNoOfImages) {
//Your Code
}
listener.onLoadTimeout = function(num, total) {
//Your Code
}
myPreloader.addLoadListener(listener);
myPreloader.addTimeoutListener(listener);