making a battery bar on touchshield slide

I'm trying to make a battery bar for my project so you can monitor the battery voltage and know when it is needs charging. Im using the touchshield slide which is programmed seperately from the arduino. I already have the code for getting the voltage and send it to the touch shield:

#define RXpin 3            //touchshield slide pins
#define TXpin 2
SoftwareSerial touchSerial = SoftwareSerial(RXpin, TXpin);
void setup(){

void loop(){
float volts = (analogRead(A0) * 5.0) / 1024;

now i need help to make the bar on the screen to decrease and increase with the a regular battery bar you see on a phone

im using this battery and this charger