Fill username and password using selenium in python

How can I auto fill the username and password over the link below:

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

chromedriver = 'C:\\chromedriver.exe'
browser = webdriver.Chrome(chromedriver)
browser.get('http://www.example.com')

After that I really do not know:

username = Select(browser.find_element_by_name('Username'))
password = Select(browser.find_element_by_name('Password'))
username.select_by_visible_text("text")
password.select_by_visible_text("text")