Q: how to reset password?

Go to http://appleid.apple.com and click 'Reset your password'. Sign in with your ID. A new password will be sent to your associated email address. Alternatively if you have set up security questions you can answer those to identify yourself.

To reset your iCloud password, you need to go into Manage Your Apple ID and change your Apple ID password (if you have more than one Apple ID, the one you would need to update would be the one that matches the email that the iCloud has). Your Apple ID is also an iCloud and iTunes ID:

https://appleid.apple.com/cgi-bin/WebObjects/MyAppleId.woa/

Cheers,

GB