do to so you should load your images into an array. like this for examples :

PImage[] images = new PImage[numFrames]; //image array

images[0] = loadImage("1.jpg");
images[1] = loadImage("2.jpg");
images[2] = loadImage("3.jpg");
images[3] = loadImage("4.jpg");  
etc etc etc

now create a variables as counter, lets say

int count =0;

that you count up when clicking

void mouseReleased(){
count++;
}

and in draw you call your image like this


image(image[count],0,0);

take care that you reset the counter when reaching the number of your images