Click on the button below to go through a demo of Keyword Transfer. To normally do it, just use the send feature in Vigenere encode and decode.
It works just like this analogy: Alice wants to send a secret message to Bob. She puts the message in a padlocked box, and sends it to Bob. Bob then puts his own padlock on the box, and sends it back. Alice removes her padlock, and sends it to Bob. Bob can now use his own key to open the box and read the message. For more about keyword transfer, go here.