Linked Lists

I am trying to understand user defined Linked Lists in C++.  I am trying to work through a lab exercise with class definitions and implementations posted by the instructor. Things were a little easier to follow when they were using the STD version. I need to store 10 strings in alphabetical order and then print them in descending order. I created the the list and stored the strings. II am  trying to figure out how to print them in descending order but can't get out the starting gate. I was checking  out the web for tutorials and how to but too much information out there. Could some kind soul lend some assistance? Here's what I got.

#include <cassert>
#include <iostream>
#include <string>
using namespace std;



class Node {
      public:
            Node(string s);

      private:
            string data;
            Node* previous;
            Node* next;
            friend class List;
            friend class Iterator;
};

class Iterator {
      public:
            Iterator();
            string get() const;
            void next();  
            void previous();  
            bool equals(Iterator b) const;
      private:
            Node* position;  
            Node* last;  
            friend class List;
};


class List {
      public:
            List();
            void push_back(string s);  
            void insert(Iterator pos, string s);
            Iterator erase(Iterator pos);
            Iterator begin();  
            Iterator end();  
      private:
            Node* first;
            Node* last;
};


Node::Node(string s) {
      data = s;
      previous = NULL;
      next= NULL;
};

Iterator::Iterator():position(NULL),last(NULL) { }
      string Iterator::get() const {
      assert(position != NULL);
      return position->data;
}

void Iterator::next() {
      assert(position != NULL);  
      position = position->next;
}
void Iterator::previous() {
      if (position == NULL)
            position = last;
      else
            position = position->previous;
            assert(position != NULL);  
}

bool Iterator::equals(Iterator b) const {
      return position == b.position;
}


List::List() {
      first = NULL;
      last = NULL;
}

void List::push_back(string s) {
      Node* newnode = new Node(s);
      if (last == NULL){
      first = newnode;
      last = newnode;
}
else {
      newnode->previous = last;
      last->next = newnode;
      last = newnode;
      }
}

void List::insert(Iterator iter, string s) {
      if (iter.position == NULL) {  
      push_back(s);
      return;
}

Node* after = iter.position;
Node* before = after->previous;
Node* newnode = new Node(s);
newnode->previous = before;
newnode->next = after;
after->previous = newnode;
if (before == NULL)  
      first = newnode;
else
      before->next = newnode;
}

Iterator List::erase(Iterator i) {
Iterator iter = i;
assert(iter.position != NULL);  
Node* remove = iter.position;
Node* before = remove->previous;
Node* after = remove->next;
if (remove == first)
      first = after;
else
      before->next = after;
if (remove == last)
      last = before;
else
      after->previous = before;
      iter.position = after;
delete remove;
return iter;
}

Iterator List::begin() {
      Iterator iter;
      iter.position = first;
      iter.last = last;
      return iter;
}

Iterator List::end() {
      Iterator iter;
      iter.position = NULL;
      iter.last = last;
      return iter;
}
int main()
{
    List soldier;
    soldier.push_back("Allen");
    soldier.push_back("Christ");
    soldier.push_back("Dog");
    soldier.push_back("Fiona");
    soldier.push_back("Jerry");
    soldier.push_back("John");
    soldier.push_back("Lion");
    soldier.push_back("Tiger");
    soldier.push_back("Tom");
    soldier.push_back("Wolf");

    cout << soldier.begin();

    system("pause");
    return 0;
}