Python UI with Tkinter

Question

I started with Python and Tkinter and am trying to make my first steps by creating a simple UI with a header, sidebar (currently just a label) and a few labels and entries.

Before I go on I want to ask you all if the way I do this is correct and a common one. Also if you see potential to make this better, please let me know!

import tkinter as tk
from tkinter import messagebox
import tkinter.ttk as ttk

class MainApplication(tk.Frame):
    def __init__(self, parent, *args, **kwargs):
        tk.Frame.__init__(self, parent, *args, **kwargs)
        self.parent = parent

        root.geometry('1280x768')
        root.configure(background='#0E2F47')

        root.grid_rowconfigure(20, weight=1)        

        s = ttk.Style()
        s.theme_use('classic')        
        s.configure('SOExample.TEntry', relief='flat')
        s.layout('SOExample.TEntry', [
            ('Entry.highlight', {
                'sticky': 'nswe',
                'children':
                    [('Entry.border', {
                        'border': '1',
                        'sticky': 'nswe',
                        'children':
                            [('Entry.padding', {
                                'sticky': 'nswe',
                                'children':
                                    [('Entry.textarea',
                                      {'sticky': 'nswe'})]
                            })]
                    })]
            })])

        # GUI elements
        header_img = tk.PhotoImage(file='Header.png')

        header_label = tk.Label(root, bg='#191E31', image=header_img)
        header_label.image = header_img
        header_label.grid(column=1, row=0, columnspan=20)

        sidebar_label = tk.Label(root, bg='#191E31', width=25)
        sidebar_label.grid(column=1, row=1, rowspan=20, sticky="nws")

        # Input Section
        adress_input_label = tk.Label(root, bg='#0E273B', fg='#CEDEEE', text="Adress", font=("Century Gothic", 12), anchor='w')                                 
        adress_input_label.grid(column=2, columnspan=3, row=1, pady=25, sticky='new')

        adress_input_entry = ttk.Entry(root, style='SOExample.TEntry')
        adress_input_entry.grid(row=1, column=3, sticky='e')

        message_input_label = tk.Label(root, bg='#0E273B', fg='#CEDEEE', text="Message", font=("Century Gothic", 12), anchor='w')                                 
        message_input_label.grid(column=2, columnspan=3, row=2, pady=25, sticky='new')

        message_input_entry = ttk.Entry(root, style='SOExample.TEntry')
        message_input_entry.grid(row=2, column=3, sticky='e')


def on_closing():
    if messagebox.askokcancel("Quit", "Do you want to quit?"):
        root.destroy()

if __name__ == "__main__":
    root = tk.Tk()

    MainApplication(root).grid(column=0, row=0)

    root.protocol("WM_DELETE_WINDOW", on_closing)
    root.mainloop()