you can see from this image, it has the button called Forgot Password. you will be redirected to a website for changing your password, and you can change your password there.
also, you need to insert your email and username that linked to your current account-- otherwise, it wont work.
after that, you will recieve an email, click the link to activate your new password, for example this link:
if the new password activation is sucsessful, you can insert the new random password below that link.
Delta Hyperion-Z's post in How can I change my password ? was marked as the answer