C++ program structure

I'm having some trouble thinking of how to structure a program in C++. I am following a book in learning C++ and at one point we construct two classes in an effort to solve a problem. The book ends up putting both classes, and how they're used all in one file and running it, and this works. But I understand more properly structured code would include header files and each class would get it's own file, and trying to structure the program like this is causing problems when I try to get the code to compile.

I have two classes, Token and Token_Stream, from other languages I know Token and Token_Stream should get their own files and that each should have a declaration file. My main issue is:

Token_Stream needs to know about Token. When a Token_Stream is initialized it initializes a Token. I had thought it would suffice to have just the declaration of Token included in Token_Stream and that would be enough, but that appears not to be the case. I know a bit about programming with OOP languages, but Token_Stream does not inherit anything from Token, nor should it (I believe) it just needs to know enough to initialize a Token and store it. I will include each of the relevant files below:

Token.h

// Token.h, declaration for Token

class Token
{
public:
    char kind;
    double value;

    Token(char ch);

    Token(char ch, double val);
}; //class Token

Token.cpp

// Token.cpp

#include "Token.h"

using namespace std;

Token::Token(char ch) 
    :kind(ch), value(0){}

Token::Token(char ch, double val)
    :kind(ch), value(val) {}

Token_Stream.h

// Token_Stream.h, declarations


class Token_Stream
{
public:
    Token_Stream();
    Token get();
    void putback(Token);

private:
    bool full; // do we already hold a token?
    Token buffer; // what Token do we hold?
};//class Token_Stream

Token_Stream.cpp

// Token_Stream.cpp implementation.

#include <iostream>
#include <stdexcept>
#include "Token.h" // needs to know what a Token is
#include "Token_Stream.h"

using namespace std;

/***********************************************************************
 * Token_Stream::Token_Stream()
 * 
 * Constructor for Token_Stream(), sets full = false and buffer as 0
 * Need to do :buffer(0), so we don't create an extra buffer variable
 **********************************************************************/
Token_Stream::Token_Stream()
:buffer(0)
{
    full = false; // nothing in our stream yet.
}//constructor

/***********************************************************************
 * void Token_Stream::put_back(Token t)
 * 
 * Given a token, we fill buffer and change full to true
 * 
 * Parameter: t - Token to fill buffer
 **********************************************************************/
void Token_Stream::putback(Token t)
{
    if(!full) // if its empty
    {
        buffer = t;
        full = true;
    }//if not full
    else
        throw runtime_error("buffer already full");
}// putback


/***********************************************************************
 * Token Token_Stream::get()
 * 
 * gets another token from input, or if we have one stored, gets that.
 * 
 * Returns: Token - next token in stream, either from buffer or from
 *                  input
 **********************************************************************/
Token Token_Stream::get()
{
    if(full) //if we already have something
    {
        full = false;
        return buffer;
    }

    //if we've reached here we haven't returned:

    char ch;
    cin>>ch; //get next input and switch over cases:
    switch(ch)
    {
        // if they input a valid character:
        case ';': 
        case 'q':
        case '(': case '+': case '*': case '-': case '/': case '%': 
        case ')':
            return Token(ch);
            break;

        //if they input a valid number, or lead with a decimal i.e., .5
        case '.': case '0': case '1': case '2': case '3': case '4': 
        case '5': case '6': case '7': case '8': case '9': 
        {
            cin.putback(ch);
            double val;
            cin>>val; //read it as a number
            return Token('8',val);
            break;
        }//case of valid number
        default:
            throw runtime_error("Bad Token");
    }//switch
}//get

So those are the files, and when I try to compile things, i.e., put a blank int main(){} in Token.cpp, everything works fine, I compile, and if I wanted to I could run things in main()

But when I try put a blank int main(){} in Token_Stream.cpp and try to compile it does not work, I am running:

g++ -Wall -std=c++11 -o "Token_Stream" "Token_Stream.cpp" 

and I am not even getting line number errors, but its claiming an undefined reference to Token::Token(char) etc and the rest of the Token constructors, so I'm guessing that this means that Token_Stream.cpp needs to see more of Token.cpp, how do I do this? Do I just simultaneously compile them?