Please help!! quick vigenere question

[tomtomisaballer]

This is my code: Vigenere cipher :

from graphics import *

##def encode(message, keyword):


def main():


    win= GraphWin("Vigenere cipher", 400,350)


    messagebox = Text(Point(100, 60), "Enter message to encode")
    keywordbox = Text(Point(63, 120), "Enter Keyword")
    encodedbox =  Text(Point(75, 250), "Encoded Message")
    message = Entry(Point(290, 60), 20)
    message.setText("")
    keyword = Entry(Point(290, 120), 20)
    keyword.setText("")
    encode = Entry(Point(290, 250), 20)
    encode.setText("")
    messagebox.draw(win)
    keywordbox.draw(win)
    encodedbox.draw(win)
    message.draw(win)
    keyword.draw(win)
    encode.draw(win)

    button = Text(Point(280, 190),"Convert It!")
    button.setOutline("black")
    button.draw(win)

    win.getMouse()
   

    message = message.getText()
    keyword = keyword.getText()
   

    message = message.upper()
   
    message = message.replace(" ","")
    keyword = keyword.upper()
    chars = []
   
    for i in range(len(message)):
       
        letter = (ord(message[i])-65)
        keyword1= len(message) / len(keyword) + 1
        keywordrepeated= int(keyword1) * keyword
        adjustedletter = (ord(str(keywordrepeated[i]))-65)
        encodedmessage= ((letter + adjustedletter)) % 26 
        encodedmessage= chr(encodedmessage + 65)
        chars.append(encodedmessage)

        encodedmessage = "".join(chars)
        encode.setText(encodedmessage)
       
       
    close = win.getMouse()
    win.close()
       
main()

I am new to functions and need to know how to create a different function called

def encode(message, keyword): <------- and how to incorporate it into def main(): so the code wont be so bunched up in the middle, Thanks!!