If an account has been accidentally set up as a student account instead of a teacher account, then don't worry! You can add the teacher role to the same account. This is done by first logging in to the student account in a web browser. While logged in as a student, go to the teacher invite that was sent to your e-mail address. Click on the "Accept invitation" button in the teacher invitation and you will automatically be taken back to the web browser where a dialogue box has appeared that gives you the option to accept the teacher role on your current account.
If you are currently on the student role, and you already have access to the teacher role, you can click on the current role in the top-left corner under the profile picture to switch roles.