If you're having trouble signing in to your account, we would advise resetting your password in order to update your account. You can do this by clicking the 'forgotten password?' underneath the sign in form, like this:
You will then be directed to the following page, where you should confirm the correct email address for the account you've forgotten the password for.
This will send you an email, to the stated address, helping you to reset your password, and you should be able to log in once that's done. Please allow up to 30 minutes for it to arrive and check your spam and junk folders.