To start using 9kw, you will need to first create an account at https://www.9kw.eu/register.html.
Then, follow the account confirmation instructions, and when logged in, navigate to https://www.9kw.eu/usercaptcha.html.
On this page, you can solve other people's CAPTCHAs to build up credit to use later on API calls. After solving a few CAPTCHAs, navigate to https://www.9kw.eu/index.cgi?action=userapinew&source=api to create an API key.