To get notified when somebody posts in a given forum, you need to adjust the notification settings for that forum.
Subscribing to a forum or topic
1. Visit the forum (or topic) you wish to subscribe to
2. Scroll to the bottom of the forum, and click the spanner icon
3. Click "Subscribe Forum" from the drop-down
Choosing what sort of notification to receive
You can choose if the notification is an email, or a message within the forum, or both:
1. Click on your name at the top right of the forum
2. Click on "User Control Panel" from the drop-down menu
3. Click on the "Board Preferences" tab
4. Click on "Edit Notification Options" in the left-side gallery
5. Tick the boxes to suit your preference, then click submit at the bottom.