You may change your username by logging in to BrightTALK then going to https://www.brighttalk.com/mybrighttalk/profile. From there you will be able to select "edit profile" and change your email address(username). Please note this will change two things:
The email address used to login to BrightTALK.
The email address where BrightTALK emails and further communications are sent.
If you have any questions feel free to email firstname.lastname@example.org for further assistance.