You will receive an email from Clio. Click the link in the email and sign into Clio to approve the change.
Now go to Settings > Manage Users and edit the same User.
Now Click on "Force Password Reset"
You will receive an email from Clio. Click the link in the email and provide a new password for this legacy account. NOTE: After doing this step, you will be logged in as the legacy user. You will likely need to sign out again.