The locked account happens when the user puts their passwords wrong more than 5 times. The user needs to wait 5 mins to be able to try again. The system will show you an error message saying: "Sorry, your account has been locked. Please try after X minutes, X seconds".
Once the account is locked, if you keep trying the system will add an extra 5 mins every time. So, If you cannot remember the password, please go to the login page and click "Forgot your password".