In order to obtain and use Test Harness application you have to register an account in this web portal.
By clicking the "Register now" button you will be redirect to the the registration form, in which you have to put your personal data, including a valid email address. When the request will be submitted, an email containing an activation link that will allow you to enter in the user area of this website will be sent to the address that you indicated in the form.
Once the registration is confirmed, you can login by clicking the user login menu, and inserting the e-mail address as user name and the password that you choose in the registration step.