control key question

how do you write to the control key I couldnt find it in the manual

You can't 'write' to the control keys... but you can read them:

function Update () {
    if(Input.GetKeyDown(KeyCode.LeftControl))
    {
        // do something
    }
}

You can get the names of these keys from:

http://unity3d.com/support/documentation/ScriptReference/KeyCode.html

Scripting reference is:

http://unity3d.com/support/documentation/ScriptReference/Input.GetKeyDown.html