trying to add texture to my code [closed]

I have been working on making a cube and I have some balls inside it though I am having problems on how I can put or add texture to my code. I am trying to learn but it seems whatever material I'm coming across is kind of confusing me. How can I add texture to this code below? This my code below

#define GL_GLEXT_PROTOTYPES
#ifdef __APPLE__
#include <GLUT/glut.h>
#else
#include <GL/glut.h>
#endif
#include <Eigen/Core>
using namespace Eigen;

struct PointMass
{
    PointMass() : pos(0,0,0), vel(0,0,0) {}
    PointMass( const Vector3f& pos )
        : pos( pos )
        , vel( 0, 0, 0 )
    {}

    void Integrate( float dt )
    {
        // "gravity" force vector
        Vector3f g( 0, 0, -2 );

        // semi-implicit euler
        vel = vel + g * dt;
        pos = pos + vel * dt;

        // collision detection/response
        if( pos.z() < 0 )
        {
            pos.z() = -pos.z();
            vel.z() = -vel.z();
        }
    }

    Vector3f pos;
    Vector3f vel;
};

GLfloat WHITE[] = {1, 1, 1, 1};
GLfloat RED[] = {1, 0, 0, 1};
GLfloat GREEN[] = {0, 1, 0, 1};
GLfloat MAGENTA[] = {0, 0, 1, 1};

class Ball 
{
    double radius;
    GLfloat* color;
    PointMass pm;
public:
    Ball(double r, GLfloat* c, const Vector3f& pos )
        : radius(r)
        , color(c)
        , pm( pos )
    { }

    void Integrate( float dt )
    {
        pm.Integrate( dt );
    }

    void Draw()
    {
        glPushMatrix();
        glMaterialfv(GL_FRONT, GL_AMBIENT_AND_DIFFUSE, color);
        glColor4fv( color );
        glTranslatef( pm.pos.x(), pm.pos.y(), pm.pos.z() );
        glutSolidSphere(radius, 30, 30);
        glPopMatrix();
    }
};

Ball balls[] = 
{
    Ball( 0.1,   GREEN,      Vector3f( 1, 1, 2 )    ),
    Ball( 0.1,   MAGENTA,    Vector3f( -1, 1, 1 )   ),
    Ball( 0.1,   WHITE,      Vector3f( 0, -1, 1.5 ) ),
};

double rotate_x = 55; 
double rotate_z = 25;   
void display()
{
    static int last = glutGet(GLUT_ELAPSED_TIME);
    int cur = glutGet(GLUT_ELAPSED_TIME);
    float dt = ( cur - last ) / 1000.0f;
    last = cur;

    glClear(GL_COLOR_BUFFER_BIT|GL_DEPTH_BUFFER_BIT);

    glMatrixMode( GL_PROJECTION );
    glLoadIdentity();
    double w = glutGet( GLUT_WINDOW_WIDTH );
    double h = glutGet( GLUT_WINDOW_HEIGHT );
    gluPerspective( 60, w / h, 0.1, 100 );

    glMatrixMode( GL_MODELVIEW );
    glLoadIdentity();
    GLfloat lightPosition[] = {4, 3, 7, 1};
    glLightfv(GL_LIGHT0, GL_POSITION, lightPosition);
    glTranslatef( 0, 0, -5 );
    glRotatef( -rotate_x, 1.0, 0.0, 0.0 );
    glRotatef( -rotate_z, 0.0, 0.0, 1.0 );


 glBegin(GL_QUADS);

  glEnd();

  // White side - BACK
  glBegin(GL_QUADS);
  glColor3f(  1.0,  0.0,  0.0 );
    glVertex3f( 1.5f, 1.5f, 1.5f);   //V2
    glVertex3f( 1.5f,-1.5f, 1.5f);   //V1
    glVertex3f( 1.5f,-1.5f,-1.5f);   //V3
    glVertex3f( 1.5f, 1.5f,-1.5f);   //V4
  glEnd();

  // Purple side - RIGHT
  glBegin(GL_QUADS);
  glColor3f(  1.0,  0.0,  1.0 );
 glVertex3f( 1.5f, 1.5f,-1.5f);   //V4
    glVertex3f( 1.5f,-1.5f,-1.5f);   //V3
    glVertex3f(-1.5f,-1.5f,-1.5f);   //V5
    glVertex3f(-1.5f, 1.5f,-1.5f);   //V6
  glEnd();

  // Green side - LEFT
  glBegin(GL_QUADS);
  glColor3f(   0.0,  1.0,  0.0 );
  glVertex3f(-1.5f, 1.5f,-1.5f);   //V6
    glVertex3f(-1.5f,-1.5f,-1.5f);   //V5
    glVertex3f(-1.5f,-1.5f, 1.5f);   //V7
    glVertex3f(-1.5f, 1.5f, 1.5f);   //V8
  glEnd();
  glBegin(GL_QUADS);
  glColor3f(   1.0,  1.0,  0.0 );
  glVertex3f(-1.5f, 1.5f,-1.5f);   //V6
    glVertex3f(-1.5f, 1.5f, 1.5f);   //V8
    glVertex3f( 1.5f, 1.5f, 1.5f);   //V2
    glVertex3f( 1.5f, 1.5f,-1.5f);   //V4
  glEnd();   

    for (int i = 0; i < sizeof balls / sizeof(Ball); i++) 
    {
        balls[i].Integrate( dt );
        balls[i].Draw();
    }
    glFlush();
    glutSwapBuffers();
}

void specialKeys( int key, int x, int y )
{
    if (key == GLUT_KEY_RIGHT)
        rotate_z += 5;
    if (key == GLUT_KEY_LEFT)
        rotate_z -= 5;
    if (key == GLUT_KEY_UP)
        rotate_x += 5;
    if (key == GLUT_KEY_DOWN)
        rotate_x -= 5;
}

void timer( int extra )
{
    // run display() every 16ms or so
    glutTimerFunc( 16, timer, 0 );
    glutPostRedisplay();
}

int main(int argc, char* argv[])
{
    glutInit(&argc,argv);
    glutInitDisplayMode(GLUT_DOUBLE | GLUT_RGB | GLUT_DEPTH);
    glutCreateWindow("Awesome Cube");
    glEnable(GL_DEPTH_TEST);
    glLightfv(GL_LIGHT0, GL_DIFFUSE, WHITE);
    glLightfv(GL_LIGHT0, GL_SPECULAR, WHITE);
    glMaterialfv(GL_FRONT, GL_SPECULAR, WHITE);
    glMaterialf(GL_FRONT, GL_SHININESS, 30);
    glutDisplayFunc(display);
    glutSpecialFunc(specialKeys);
    glutTimerFunc( 0, timer, 0 );
    glutMainLoop();
    return 0;
}

Secondly when I write this code below in the main function

glEnable(GL_LIGHTING);
glEnable(GL_LIGHT0);

The walls of the cube turns grey any expalination why I'm getting this??