Click on the "Log in" button and then on the link "Forgot your password?

If you remember your e-mail address, enter it and click on the "Request" button. You will shortly receive an e-mail with a link to reset your password. Use the e-mail address and the new password to log in. If you do not remember your e-mail address, you can use the tax code/VAT field and click on the "Request" button.

If you don't see the email in your inbox, try checking your junk mail.