Tapjoy comes with an example application called the EasyApp. You can add your own SDK key and placement names to it to test your dashboard setup is correct, and you can review the code to better understand how to integrate Tapjoy with your application.
When you download the iOS SDK the EasyApp comes with it in a folder labeled 'TapjoyEasyApp'.
You can open the project in Xcode and immediately build & run.