How to do it...

This snippet creates a main window with a custom title and icon. It has 400px of width by 200px of height, with a separation of 10px in each axis to the upper-left corner of the screen:

import tkinter as tk 
 
class App(tk.Tk): 
    def __init__(self): 
        super().__init__() 
        self.title("My Tkinter app") 
        self.iconbitmap("python.ico") 
        self.geometry("400x200+10+10") 
 
if __name__ == "__main__": 
    app = App() 
    app.mainloop()

This program assumes that you have a valid ICO file called python.ico in the same directory where the script is placed and executed.