On the Discussions List page, from the context menu of the forum or topic you want to receive notifications of new posts for, click Subscribe.
On the View Topics page, beside the thread you want to receive notifications for, click Subscribe.
In the Customize Notifications pop-up window, select your Notification Method. If you do not have an email address set up in your user profile to receive notifications, in the Customize Notifications pop-up window, click the Add an email address in a new window link. Click the Enable email notifications link, then set your email preferences in the Email Settings pop-up window. Click Save.