If you signed up for your Schoolhouse account with a username/password, you can click the "Don't remember your password?" option on the sign-in page to reset your password. From there, you'll receive an email with reset instructions.
If you don’t receive an email with reset instructions, here are a few things to check:
Look in your spam or junk folder. The email might have been filtered there.
Double-check that you're looking in the correct email inbox. Make sure you're using the email address associated with your Schoolhouse account.
Please note that if you sign into Schoolhouse using your Google account, you will NOT receive a password reset email.
More information on how you can reset your password can be found here.