[@Maglar] You don't write or post on their website, you just keep track of your wordcount. They provide the tools to help you reach the goal, but you have to use your own preferred software, or pen and paper if you wish, to write your story.

On the 1sth you can change your story from 'prepping' to 'in progress' and the option to add your wordcount should be accessible. 
If you update daily you can claim badges, there is a badge for updating the wordcount for 30 days in a row.