How do i make my bulletSpawn become a parent of something

bulletSpawn = transform.Find (“bulletSpawn”);

How do i make my bulletSpawn become a parent of something

Transform.parent does the trick. The documentation provides an example, so it shouldn’t be difficult to adapt it to your situation.

You need to use Transform.parent.

var parent : Transform;
var bulletSpawn : Transform;

function Start () {
     bulletSpawn = transform.Find("bulletSpawn");
     bulletSpawn.parent = parent;
}

Edit: Thanks to schnaddlbraag for pointing out that the above example makes the bulletSpawn a child of the parent object. If you want to do the reverse, use

var child : Transform;
var bulletSpawn : Transform;

function Start () {
     bulletSpawn = transform.Find("bulletSpawn");
     child.parent = bulletSpawn;
}