You should have received an email introducing you to this Customer Portal. This email should contain your Job Number as well as a link to set your password.
If you have both your Job Number and your Password, enter them in the login form and hit submit.
If you no longer have your Invite email and no longer remember your password, hit the "Click here to reset password" link near the submit button of the login form.
You will be prompted for your Job Number, enter this and submit.