Once you are done creating a Phonebook and importing/adding contacts to it, you can now create a SMS campaign from section Interconnection > SMS Campaigns. Click on Add New button on the left hand side and this will take you to a page for creating campaign.
You need to give it a Name, select one of the Tollfree Phone Number on which SMS is enabled (If SMS is not enabled you can activate it from section Phone Numbers) and enter the content in section Text Message and select one or more Phonebooks.
After you click Create, it will give you more options as shown in image below to schedule the campaing.
Frequency - This will decide that how many times you want to send per minute.
Max Retry - This will set the number of retry in case your SMS fails for any reasons.
Week Days - Toggle the on/off to enable the days on which the SMS is sent.
Start/Finish - This will set the start and end date date of your SMS campaign.
Daily Start/Stop Time - This will enable you to set a time frame between which the campaign will run.
Click Save to apply the changes. You will be taken to campaign page. To start your campaign click play button.