This feature is off by default. To use it go to the MyProfile page. As a part of the profile you can now fill in your 10-digit cell phone number, select your carrier (currently only ATT & Verizon), and set if you want to receive the notifications (CellNotify). The number and carrier are good for all forums, so only need to be set once.

The CellNotify function is then set to true or false for each forum. You need to be editing your profile in the forum you wish to receive cell notification from to set it true or false for that forum.

The text message received indicates who sent you the message and an active link to the forum where the message was posted. With a smart phone you just click on the text message link and the browser will open and take you to the forum.