simple script that changes scenes when trigger is touched by the unity default first person character controller, and how to use it
All is in documentation, if you put a little bit of effort, and paste here any script of yours I would fix it, otherwise can just send you to documentation.
Triggers
http://docs.unity3d.com/ScriptReference/Collider.OnTriggerEnter.html
http://unity3d.com/learn/tutorials/modules/beginner/physics/colliders-as-triggers
Change level
http://docs.unity3d.com/ScriptReference/Application.LoadLevel.html
This is Script will assign to trigger object.
void OnTriggerEnter(Collider Other)
{
if(Other.CompareTag(“Player”))
{
Application.LoadLevel(“YourScene”);
}
}