Dragon Valley can be a little weird. It won't show up in your Origin account usually. You'll have to log into thesims3.com nd head to your purchase history, where Dragon Valley should be available to download. After it's downloaded you'll have to launch your Sims 3 game, head into the main menu and look at your Downloads Dashboard. Dragon Valley should be listed there, available to install.
Alternatively, you can check out downloads section in The Sims 3 Launcher and the world may appear there, available to install.
Dragon Valley is a world available to play in, and you wshouldn't see Dragin Valley content in a game you've already started. You will have to start a new game to see Dragon Valley as a place to start.
