Click this link to go to http://account.nokia.com, sign in, and follow the instructions.
If you decide to change your password for your Nokia Mail account, you must first change the password in any mobile device or mail client program settings to retrieve email and then change your password in your account before you use these devices or programs to retrieve your mail again. Mail client programs have password settings that can use Post Office Protocol, otherwise known as POP, to retrieve messages.
If you neglect to change the passwords in the these places in the correct order, the situation gets tricky because some mobile devices and mail client programs perform access to your mail account just after you start the program, and repeated attempts result in a lock on the account. We put a lock on the account because someone's email client, yours, has asked for mail with the wrong password too many times.
So before you change your password with Nokia, first disable automatic retrieval and then change the password on each and every one of the mobile devices and mail client programs you use on that account. Nokia Mail does not get enough security information to deal with your device and program passwords not being coordinated with your genuine account password, so to be secure, Nokia Mail locks the account until you put the account through a re-verification process.