In order to change your account password you need to go to the login page and enter your email address. After that you will se a button that says "Forgot password?", click on it and and submit your email address:

After that you will receive an email to reset your password that works only for the next 30 minutes, so make sure you change your password on time.

Quick note: some users don't have password and are only able to login with a one time sign-in email. If you don't receive that email please contact support.