If you signed up for Inspector Toolbelt using your Google account, then your profile information is maintained through your Google account. This also includes your password.
If you would like to make updates to how your name is displayed, or to your password, please make the changes using your Google account. The next time you sign out and back in to Inspector Toolbelt, the changes will reflect in your Profile Information.
At this time this time it is not possible to change the Google account used to register your account with Inspector Toolbelt. If you would like to use another account, you would have to sign up again.
For more information on updating your profile information with Google, please see this article: Change your Google Account name & other info