How do you insert a value at the end of a LinkedList?

I'm trying to add a value given to the end of a LinkedList. I know how to iterate to the end of the LinkedList but I'm not sure where to go from there.

void llist_insert_last(LinkedList * list, int value) {
  ListNode * e = list->head;
  while(e != NULL) {
    e = e->next;
  }
}