You will find in right hand side boxes for username and password enter your login name and password over there.
Step3
Now after logging in right top corner there is link for 'Settings' click on it that will open settings panel (u will find there General, Accounts, Labels etc).
Step4
In that click on second tab 'Accounts' will open 'Accounts' tab in that click on -->'Google Account Settings'(4th in vertical order).
Step5
This will open one window containing Personal information. There is link for change password. Click on it
Step6
Then put your current password and then new password and then click on 'Save' button.