If you are using the Professional Edition of ZOHO, it doesn't support creating new modules and buttons. This lack of permission doesn't allow you to use SMS Magic in your ZOHO org, as we have to create various buttons and modules in your org, as a part of the basic setup.
Supposing that you chose to try SMS Magic and have proceeded towards the configuration, you would need to configure these:
"Send SMS" button on the detail page for Leads and Contacts
- "Send Bulk SMS" buttons on the list view of Leads and Contacts
- Three new modules: "SMS History", "SMS SenderID" and "SMS templates" for storing the necessary SMS logs