Note: an updated version of this tutorial is here http://gamefroot.com/purchasing-asset-packs-from-the-marketplace/
Every game has to have assets! These are the images, animations, characters, terrain, items, buttons, sound effects, music, and scripts that are used to build your game. You can create your own assets, or you can grab an asset pack from the Marketplace. Most of them are free, and they can be used to quickly make a game. Here’s how: