BST Tree

I am trying to input these values into a BST but I am not sure where to start. Here is what I have:

client file

#include<iostream>
#include<iomanip>
#include<fstream>
#include <cctype> // defines isalpha() function

#include"t.cpp"

using namespace std;

int main()
{

btree bt;
int num=0;
char chr;
int count=0;

ifstream fin("input.txt");
ofstream fout("output1.txt");

fin>>num;
fin>>chr;
while(fin)
{

count++;
fout<<"Step: "<<count<<" "<<"Data Value = "<<num<<" "<<"Activity Signal = "<<chr<<endl;

fout<<"Preorder Transversal = "<<endl<<endl;
fout<<"Inorder Transversal = "<<endl<<endl;
fout<<"Post order Transversal = "<<endl<<endl;
fout<<"Level by Level Transversal = "<<endl<<endl;
fout<<"Total Number of nodes = "<<count<<endl<<endl;

fin>>num;
fin>>chr;
}

return 0;
}

Implementation file

#include "t.h"
#include <stddef.h> // For NULL

struct TreeNode {
char data; // Data member
NodePtr lLink; // Pointer to left child
NodePtr rLink; // Pointer to right child
TreeNode( char, NodePtr, NodePtr ); // Constructor
};

TreeNode::TreeNode( /* in */ char someChar,
/* in */ NodePtr leftPtr,
/* in */ NodePtr rightPtr )
//.................................................. ................
// POST: data == someChar && lLink == leftPtr && rLink == rightPtr
//.................................................. ................
{
data = someChar; lLink = leftPtr; rLink = rightPtr;
}

// Private members of CharTree class:
// NodePtr rootPtr; Pointer to root node

btree::btree()
//.................................................. ................
// POST: rootPtr == NULL
//.................................................. ................
{
rootPtr = NULL;
}

bool btree::IsEmpty() const
//.................................................. ................
// POST: FCTVAL == (rootPtr == NULL)
//.................................................. ................
{
return (rootPtr == NULL);
}

void btree::BuildRoot( /* in */ char someChar )
//.................................................. ................
// PRE: rootPtr == NULL
// POST: rootPtr points to newly allocated node, call it N
// && N.data == someChar && N.lLink == NULL && N.rLink == NULL
//.................................................. ................
{
rootPtr = new TreeNode(someChar, NULL, NULL);
}

NodePtr btree::Root() const
//.................................................. ................
// POST: FCTVAL == rootPtr
//.................................................. ................
{
return rootPtr;
}

void AppendLeft( /* in */ NodePtr ptr,
/* in */ char someChar )
//.................................................. ................
// PRE: ptr != NULL && Assigned(someChar)
// POST: ptr->lLink points to newly allocated node, call it LC
// && LC.data == someChar && LC.lLink == NULL && LC.rLink == NULL
//.................................................. ................
{
ptr->lLink = new TreeNode(someChar, NULL, NULL);
}

void AppendRight( /* in */ NodePtr ptr,
/* in */ char someChar )
//.................................................. ................
// PRE: ptr != NULL && Assigned(someChar)
// POST: ptr->rLink points to newly allocated node, call it RC
// && RC.data == someChar && RC.lLink == NULL && RC.rLink == NULL
//.................................................. ................
{
ptr->rLink = new TreeNode(someChar, NULL, NULL);
}

char Data( /* in */ NodePtr ptr )
//.................................................. ................
// PRE: ptr != NULL && Assigned(ptr->data)
// POST: FCTVAL == ptr->data
//.................................................. ................
{
return ptr->data;
}

void Store( /* in */ NodePtr ptr,
/* in */ char someChar )
//.................................................. ................
// PRE: ptr != NULL && Assigned(someChar)
// POST: ptr->data == someChar
//.................................................. ................
{
ptr->data = someChar;
}

NodePtr LChild( /* in */ NodePtr ptr )
//.................................................. ................
// PRE: Assigned(ptr)
// && (ptr != NULL) --> Assigned(ptr->lLink)
// POST: FCTVAL == NULL, if ptr == NULL
// == ptr->lLink, otherwise
//.................................................. ................
{
return (ptr==NULL) ? NULL : ptr->lLink;
}

NodePtr RChild( /* in */ NodePtr ptr )
//.................................................. ................
// PRE: Assigned(ptr)
// && (ptr != NULL) --> Assigned(ptr->rLink)
// POST: FCTVAL == NULL, if ptr == NULL
// == ptr->rLink, otherwise
//.................................................. ................
{
return (ptr==NULL) ? NULL : ptr->rLink;
}

bool IsLeaf( /* in */ NodePtr ptr )
//.................................................. ................
// PRE: ptr != NULL
// POST: FCTVAL == (ptr->lLink == NULL && ptr->rLink == NULL)
//.................................................. ................
{
return (ptr->lLink == NULL && ptr->rLink == NULL);
}

void DeleteLeaf( /* inout */ NodePtr& ptr )
//.................................................. ................
// PRE: Assigned(ptr)
// POST: *ptr deallocated
//.................................................. ................
{
delete ptr;
}

Input file

85 A
14 A
77 A
46 A
94 A
18 A
89 A
42 A
94 A
75 A
89 D
97 A
10 A
92 A
77 D
90 A
14 D
121 A
42 A
85 D
94 D

How do I start or insert the numbers?