When you create a new password, make sure that it's at least 8 characters long. Try to use a complex combination of numbers (NOT date of you birth), letters, and punctuation marks (like "!", "?", ";"). This will help to keep your account safe and secure.
If you would like to change your password click cog in the top right corner, choose Settings -> General. Here you can change your current password into new one.
Here you can find some information that help you keep your account safe and secure:
If you cannot login into your account and you think that it could taken over by someone else? Please report it here - Support.