To update your password in Explorer you will need to log into the application with your current username (email) and password.
In the upper-right hand corner of the Home page, use the drop down button next to your name and select 'My Profile".
This will display your profile. Here you can update your password by clicking the "Change password?" checkbox in the Login Information section. You will need to enter your current password then enter the new password in the "Password" and "Password confirmation" fields. Be sure to select a password that is secure and easy to remember. Once entered select the "Save" button at the bottom of the page.