i would like to know how to make an item that you can equip to your player for example: Super Mario and mushrooms.
Please read the tutorials, especially this one: http://unity3d.com/support/resources/tutorials/fpstutorial
Part 2 should explain in detail what you need.
EDIT: more useful links: http://forum.unity3d.com/viewtopic.php?t=28433
http://answers.unity3d.com/questions/4897/how-can-i-start-learning-unity-fast-list-of-tutorials