Start on the Backline login page.
Step 1: Click Forgot Password? on the login page.
Backline login page (click to enlarge)
Step 2: Enter your Email Address and press Reset.
Password reset window (click to enlarge)
Step 3: You will receive an email with a subject line that reads: [External] Backline Password Reset. Follow the instructions outlined in the email.
Email subject line (click to enlarge)