Help with RoMeo V2[R3] and 6V 40RPM 10kg-cm - DC Motor

This is the code:
int E1 = 5;    //M1 Speed Control
int E2 = 6;    //M2 Speed Control
int M1 = 4;    //M1 Direction Control
int M2 = 7;    //M1 Direction Control

void setup(void){
  Serial.begin(19200); 
  pinMode(4, OUTPUT);
  pinMode(5, OUTPUT);
  pinMode(6, OUTPUT);
  pinMode(7, OUTPUT);
}
void loop(void){
  analogWrite (E1,a); 
  digitalWrite(M1,HIGH);
  analogWrite (E2,b);
  digitalWrite(M2,HIGH);
}