You can create SMS Templates for any Salesforce Object that has a Phone field. To create an SMS Template, first click on the SMS Template Tab and then click on the New button.
Give your template a name, select the Object that the Template relates to and then enter a message for the Template (including using Merge Fields if required). Make sure you also select the Default Phone Field and the Senders Account for the Template. 
Note: If you wish to add merge fields to an SMS Template, you need to follow the steps below:
- Select the Object. This is the Object that the Template will be used on. You need to create specific Templates for each Object you wish to send SMS messages from. Selecting an Object automatically generates the fields that are available for merge for that Object.
- Select the Field you wish to merge
- Click the ‘Insert Text’ button
This will merge the correct merge field code into the Message text box. Once the SMS Template is complete, click Save.