You can reset your office 365 password by going to the link below and logging in with your account.
https://account.activedirectory.windowsazure.com/ChangePassword.aspx
If the above this does not work you can follow the steps below:
1) Login to http://portal.office.com
2) click on the cog wheel icon between the bell icon and question mark
3) Under settings select password change your password.
If you are not able to login please contact the support desk