To turn on your email notifications, follow these steps:
1. Navigate to your profile settings by clicking your profile avatar (in the top-right corner of your screen) and then Settings
2. You will be brought to the "options" area at the top of the screen
3. Check that your preferred email address is entered correctly, and check both enable email contact and enable HTML emails.
4. If you have a minute, scroll through the settings page to check that the rest of the settings on this page match your preferences.
To customize your email notifications, follow the instructions on this help page.