To start receiving Yapta Alerts on Twitter: 

Log into your Yapta.com Account
Click on Yapta Settings
Add your Twitter User Name
Select Receive Message via @reply or Receive Messages via Direct Message (private) depending on your settings
In your Twitter Account you can also follow @YaptaAlerts

From this point forward Yapta’s alerts will generate a "Tweet" (a Twitter Message) and an email alert if the price drops or if you become eligible for an airline travel credit.