Well first check if flash player even detects the webcam. Right click on the game and click settings. Then click on the webcam icon on the bottom on the menu. Make sure "allow" is checked so the game can use you webcam. If you have used a different webcam on your computer before, select your current webcam in the dropdown.

The second step is to adjust the settings is the game. Try putting your settings on high for best performance.

If it isn't working after this make sure the room has light in it and there isn't any motion behind you. To accomplish the 3d effect, use your body to lean left to right to look around the room.