Please follow these steps to change the password:
1) Sign in to your account with username and password.
2) There will be a option “Sign-in & security” and select choose password.
3) Enter your new password and click “ change password”.
I hope this will work to overcome your problems.
Hey you just need to follow some steps to change Gmail account paasword.
You can visit here to watch out those steps reuired to change password. It will help you to fix this issue.