I can't help you but I will give you a * till some one comes along to help you.

The first step is a picture, either an artwork of your own, scanned in or a FREE clipart. Depends on what you are going to do with it. Nobody can prohibit to digitize a Snoopy or some copyrighted material for your own. But you are not allowed to give this to others, sell it or sell embellished items with those characters. So better use a free one or a picture of your own to avoid inconvenience.
Then you will need a special software for the digitizing process and the really good ones cost really money- which is the best for you maybe depends on the machine you are going to use.
Some brands have their own compatible software.
But this is not so important- the principles of digitizing are the same.
A free one and good enough to learn the principles is Thredworks. They have lessons available on their website, a handbook, which you can download and print out to have it handy while "programming".
A hard job, I can tell you- but fun!
Here is the link, click download area. And browse around, you can learn a lot here.