BSTree add function - c++

Question

I am trying to do the add function in BSTree.However, I have no idea where to start. Can anyone give me some hints which part I need to consider first. I don't know where is the new Pair(key, value); to use and what is the using Tree::data;. I just want to get the hints but not the answer. Thank you.
Below is the Pair.h file
#ifndef PAIR_H_
#define PAIR_H_
//a key-value pair
//this simple class is pretty much self-explanatory
//all its implementation is already given
template<typename KeyType, typename ValueType>
class Pair
{
public:
Pair(KeyType k, ValueType v) :
key(k), value(v)
{
}
KeyType getKey() const
{
return key;
}
void setKey(KeyType key)
{
this->key = key;
}
ValueType getValue() const
{
return value;
}
void setValue(ValueType value)
{
this->value = value;
}
private:
KeyType key;
ValueType value;
};
#endif /* PAIR_H_ */
Below is the Tree.h
template<typename Container, typename KeyType, typename ValueType>
class Tree
{
public:
virtual bool add(KeyType key, ValueType value) = 0; //pure virtual function here, description can be found in BSTree class
virtual bool remove(KeyType key) = 0; //pure virtual function here, description can be found in BSTree class
virtual ValueType getValue(KeyType key) = 0; //pure virtual function here, description can be found in BSTree class
virtual ~Tree(){}; //an empty destructor
protected:
Container data; //the data container (a vector, which is either a ListVector or ArrayVector in this assignment)
//that stores all the node data of the tree
//how the node is stored in the data container is very specific
//please refer to the webpage description for details
//treeToString in Utility is this class's only friend... :(
template<typename aContainer, typename aKeyType, typename aValueType>
friend string treeToString(Tree<aContainer, aKeyType, aValueType>* tree);
};
#endif
Below is the BSTree.h file
#ifndef BSTREE_H_
#define BSTREE_H_
#include "Tree.h"
#include "Pair.h"
#include <typeinfo>
using namespace std;
//the Binary Search Tree class
//the keys have to be unique in the tree - you need to make sure of that when performing the insertion
template<typename Container, typename KeyType, typename ValueType>
class BSTree : public Tree<Container, KeyType, ValueType>
{
public:
BSTree(){};
~BSTree();
//add a node to the tree, according to the given key and value
//you have to use the exact algorithm described in the lecture notes
//so that you will have the exact same result as our demo and sample output
//it should do nothing to the tree and return false when there is already a node that has the same key
//otherwise, it should add the node and return true
//hint: you probably will have a statement to allocate the space for the new pair, like so: "new Pair<KeyType, ValueType>(key, value);"
bool add(KeyType key, ValueType value);
bool remove(KeyType key);
ValueType getValue(KeyType key);
int getHeight();
using Tree<Container, KeyType, ValueType>::data;
};
#include "BSTree.tpp"
#endif /* BSTREE_H_ */