There are a lot of e-card companies available online - just type in free e-cards in the search engine and take your pick. Once you find a card you like there is really nothing to the process, just fill in the blanks. You will put in the name of the person you are sending it to, a short message, and then your name. Then you will click a button to preview the card and if you like what you see then all you need to do is enter the email address of the person you are sending it to and click send.
From what I know the easiest way to create a Christmas ecard is through 123 Greetings. All you have to do is select the ecard that you like the most and then it will walk you through the rest of the process.