Accessing Child GameObject

I know there must be a simple solution to this, but I can’t seem to figure it out. I have an object attached to an NPC, and I want to access it so as to enable and disable it through the script on the parent. How do I go about this?

Try this

Transform aChild = transform.FindChild( "child name" );

if( aChild != null )
        Debug.Log( "Found child" );
        aChild.gameobject.SetActive( true ); // false
else Debug.Log( "Child not found" );

Attach it to the parent