First you need to sign up for codepen.
Codepen is completely free for what we are going to use it for. first you need to click sign up and then select the free option
Add your info and you can have a free account.
to create go up to the top right of the screen and click create.
then click new pen, this will give you a new working enviroment
and you are all set to start coding.
This is a brief example of how to use codepen