Once you have signed up and registered with the system, you can create a request. The first time you login to the system with your new account, you'll be prompted for a password, but of course, you don't have one yet. So to set up a password, at this point, begin by clicking the "forgot your password" button, which will take you to a "Forgot Password" screen that prompts you for your email address. The system will then send you an email with a link to the Change Password page, where you can create a password.
Step-by-step instructions are included in this short powerpoint deck (beginning on slide 3).