As we know Selenium is a tool used for controlling web browsers through a program. It can be used in all browsers, OS, and its program are written in various programming languages i.e Java, Python (all versions). 

Python is a powerful programming language that can be used for various tasks, including automation. One common task that can be automated using Python is posting birthday wishes on Facebook. Here, we will use Selenium, a popular web automation tool, to automate the process of posting birthday wishes on Facebook.

To get started, you will need to install the Selenium package in Python. You can do this using the pip command: 

pip install selenium

Once you have installed Selenium, you will also need to download the appropriate web driver for your browser. For example, if you are using Chrome, you will need to download the ChromeDriver. You can download the appropriate driver from the Selenium website.

Next, you will need to write a Python script that uses Selenium to automate the process of logging into Facebook, navigating to the birthday notifications page, and posting a birthday wish.

The script should start by importing the necessary modules: 

from selenium import webdriver
from selenium.webdriver.common.keys import Keys
import time

Next, you will need to create an instance of the web driver: 

driver = webdriver.Chrome('/path/to/chromedriver')

Replace "/path/to/chromedriver" with the actual path to your ChromeDriver executable.

You will also need to define your Facebook credentials: 

email = "your_email"
password = "your_password"

Then, you can use Selenium to automate the process of logging into Facebook: 

driver.get("https://www.facebook.com/")
email_elem = driver.find_element_by_id("email")
email_elem.send_keys(email)
password_elem = driver.find_element_by_id("pass")
password_elem.send_keys(password)
password_elem.send_keys(Keys.RETURN)

Next, you will need to navigate to the birthday notifications page: 

driver.get("https://www.facebook.com/events/birthdays/")

Finally, you can use Selenium to automate the process of posting a birthday wish: 

message = "Happy birthday!"
textarea = driver.find_element_by_css_selector("textarea[placeholder='Write a wish…']")
textarea.send_keys(message)
post_button = driver.find_element_by_css_selector("button[data-testid='react-composer-post-button']")
post_button.click()

You can put all of this code together in a Python script and run it to automate the process of posting birthday wishes on Facebook.