You can check the email address you have used for registration in Firstbeat Life application Profile - Settings- Account view, example picture below
If you are logged out from the application, you can check the email address by using the Forgot password? -option on the login page. Enter your email address and press Send recovery code -button. If the email has not been registered into Firstbeat Life, you will receive an error message, example picture below
If the email is regognized, the app will automatically guide you forward to the password change. Please note that it is not necessary to change the password, you can go back to the login page by using phone's Back -option.