If your Khan Academy account was created using Facebook or Google single sign-on, your password is the same one you use to log in to those services. You can reset your password directly through Facebook or Google.
If you have a Khan Academy account and forgot your password, visit this link.
Once you enter your email address and click on Reset password, a unique URL will be sent to your inbox. By accessing that URL, you will be prompted to set a new password. If you do not receive the email, check your spam folder.
If you are logged into Khan Academy already, visit your account settings.
Once you have clicked on Change password, you will need to verify your account by typing in your current password, or by authenticating through Google or Facebook.