error in activation

I have been reading the forum Re error in activation. I have tired to deauthorise my account but the ID email is not what I originally set as my new email is automatically default. My password is now no longer valid. How can I change my password so I can de authorise with the default ID email address ie my alternate email address? (it is  I am not very computer literate and am working with Windows 8.1 I hope this makes some sense. Thanks for your time