Simply install Tweeter and in your dashboard you will see a 'Surefyre Design' menu tab in the left-hand links area. Clicking this will take you into a subpage where Surefyre Design adons can be managed. You will see a 'Tweeter' tab at the top which you can click to alter Tweeter's settings.
The first time you set up Tweeter you'll see some red text telling you to authorise your site with your Twitter account. Click the link at the end of the message.
Once you've authorised with Twitter simply check the boxes to enable Tweeter to create tweets for page updates and/or new page creation and enter some prefix text. Click the 'Update' button and you're done!