How to switch off the auto-notification of email?

Hello, I became a new member of this discussion board today. After establishing an account, I was offered to take a short tour of the site. In the "Activity" section, it was noted that I would be automatically notified via my email, when my question/post had been responded to. It also showed a way to turn this automatic notification off. I went to the Activity tab, but saw nowhere to execute this option. How do I do this? I do not want auto-notification.

Thank you.