how open project unity?

hI all, i downloaded the Game Development Walkthrough from unity3d. i name the folder unity3dtutorial. and when i open from unity whith open project i target the folder unity3dtutorial. it open, i can see all assets, animation,audio, fonts, etc. but when play no run the game. in tab hierarchy there are only main camera.

either donwloaded other project direct to unity3d i play and run the game, but when close unity3d and open this last proyect no run and i can see all files in tab folder, but not in tab hierarchy