Keep pressing the widget and eventually you'll start. The goal is to get your runner across the finish line. Some races you have to click furiously to get up a hill, in others you have to click to jump. You'll get the hang of it even without Japanese. To get the code, go to the widget's webpage. Above the red button [タグを発行する」, first choose a location (any is fine) and then enter a name you want for your athlete. Then, click on the red button and the code will generate in the box below.