Correcting or changing student/parent information in an existing account is very easy. Log in with the, student email and password at www.TotalRegistration.net, click the service you need to update (AP, PSAT/NMSQT, or IB), and click Edit Student/Parent Info, as shown in the below screenshot. All of the information that is editable can be modified here.
If there is some portion of the record that you are not able to edit that needs modification, you will need to contact the school to ask them to edit the information through their account.