Add CheckBox to a Canva Kivy

I need to add a checkbox to this Kivy Canvas but it don"t know how to do it properly. I need the checkbox to display the name of all the file in the folder Data. Then the user check the file he wants and then by pressing a button (here the red one) it return a list of the file name and call some functions. Here is where i am right now.

from kivy.app import App
from kivy.core.window import Window
from kivy.uix.image import Image
from kivy.uix.widget import Widget
from kivy.metrics import dp
from kivy.lang import Builder

from kivy.uix.label import Label

from kivy.uix.button import Button
from kivy.base import runTouchApp

from kivy.uix.recycleview import RecycleView

from kivy.uix.popup import Popup



from kivy.uix.progressbar import ProgressBar 
from kivy.uix.boxlayout import BoxLayout
from kivy.clock import Clock
from kivy.uix.button import Button
from kivy.uix.popup import Popup
from kivy.uix.widget import Widget.
from kivy.properties import ObjectProperty




 import time
 import os

Builder.load_string('''<Game>
    ShootButton:


<ShootButton>

    Image: 
        source: 'logo.jpg'
        allow_stretch: True
        size: 300,300
        pos: 300, 400


    Image: 
        source: 'livre.jpg'
        allow_stretch: True
        size: 350, 350
        pos: 490,130

    Button:
        text: "Modifier Correspondance"
        size: 240,50
        font_size: 20
        pos: 100,300
        background_color :0, 1, 0, 1,
        on_press: root.shoot()

    Button:
        text: "Liste Fichiers"
        size: 240,50
        font_size: 20
        pos: 100,400
        background_color :0, 1, 0, 1,
        on_press: root.fire_popup()

    Button:
        text: "Ajouter Fichier"
        size: 240,50
        font_size: 20
        pos: 100,200
        background_color :0, 1, 0, 1,
        on_press: root.shoot2()

    Button:
        text: "Generer PDF"
        size: 180,50
        font_size: 20
        pos: 580,60
        background_color :1, 0, 0, 1,
        on_press: root.display()



         ''')


 Window.size = (900, 600)
 Window.clearcolor = (1, 1, 1, 1)




class Game(Widget):
    pass


class SimplePopup(Popup):
    pass

class SimplePopup2(Popup):
    pass

class ShootButton(Widget):

    def shoot(self):
        shooting = Bullet()
        shooting.bullet_fly()

    def shoot2(self):
        shooting = Bullet()
        shooting.bullet_fly2()

class Bullet(Widget):
    def bullet_fly(self):
        print("test")


    def bullet_fly2(self):
        os.system("open .")





class MyApp(App):
    def build(self):
        return Game()

if __name__ == '__main__':
    MyApp().run()