N.B. The screenshots and descriptions are for the iPhone/iPad version.
You can log out by going to the User Screen (the top right icon on the Home Screen) and tapping the button at the bottom of that screen. You will need to enter your email address and password to log back in. (You can view your password by tapping on the eye icon in the User->Security screen).
Tap on the 'Forgotten Password?' link on the login screen and enter the email address you normally use to sign in. If you have an account, you will then receive an email with a temporary password.
Once you have used the temporary password to log in, it will expire.