GET AUTHENTICATION DETAILS FROM TWILIO
First login to your Twilio Dashboard to retrieve Account SID and Auth Token
Next get a valid sender ID. Note: You will need to purchase atleast one Phonenumber from Twilio to be able to send SMS.
Go to the Phonenumbers tab on the left and take one of your purchased number as sender ID.
Note: Sender ID should be entered without - which is present in the web interface.
Now configure the above details on the Global SMS configuration ( Dashboard -> SMS Settings) or Site Specific SMS Configuration ( Site -> Settings -> Extra Settings)