Change your Google Account password
To change the password for your Google Account, just follow these steps:
Visit the Google Accounts security tab.
If you're not already signed in to your Google Account, enter your username and password, and click Sign in.
Click Change your password.
If you're unable to sign in to your Google Account, or you've forgotten your password, just enter your username on the password-assistance page to reset your password and regain access to your account.
Account Activity
Detecting suspicious activity on your account
Account Activity Beta
Basics: Google Web History
Change your Google Account password