If your email address in use is not correct you will need to do one of the following:
If your school are using an MIS system with synchronisation to Classroom Monitor:
Ask your school to update their MIS system to include the correct email address
If you have logged in previously and still have access to the inbox of the email address in use but need to change your email address:
Log in, go to Settings and click 'Change Email'
If you have logged in previously but do not have access to the inbox of the email address in use or if you are yet to log in and need to change your email address:
You will need to have a new user record created by somebody with Admin/SLT access in your school.