2d spawning problem

Im in middle school doing a project for a program called TSA and what Im doing currently is trying to figure out how to make an object spawn and disappear at a certain point. PLEASE HELP!!!

You can create prefabs in Unity that you can instantiate multiple times. These instances you can delete by different rules. When you search by the tag 'instantiate' you can find several questions and answers concerning this problem.

Another place to start could be the video tutorial series you can find under http://forum.unity3d.com/viewtopic.php?t=39327 There the principles of creating and deleting instances of prefabs in a simple 2D game is explained.