Here is the step by step video on how to send message on creation of lead on marketo

With the SMS-Magic App, you can send SMS on lead creation, lead updation, lead activity events and also run text drip campaigns to engage with your prospects and customers. You have to first install the SMS-Magic app from the app exchange and register and configure this application on your Salesforce instance.

Companies have multiple venues from where they collect inbound leads. Let us consider the scenario where users have a setup scheduling demo lead forms on their website and they collect demo leads. Once you fill up a lead form and submit it, the lead directly goes to the Salesforce and the Salesforce syncs the leads to the Marketo instance. Now to welcome this lead and trigger an SMS, we have to set up a converse app, which is basically setting up an automation. 

• To set up the converse app, create your templates and choose your Sender ID before triggering a message that would define what kind of message has to be triggered
• We can add multiple templates in the Converse app and define what action has to be taken on those messages. Through the Sender ID, users who are going to book the demo will receive a message upon booking the demo. 
• In the next step, copy the action key and create a task in Marketo. Marketo will understand the action of any event, like booking a demo for that particular lead.
• In the next step, in the smart campaign, define to whom the message is to be sent, what message, when it will be sent, and the results.  
• In the smart list, build a very basic Trigger, a smart campaign, and check if a person is created as a lead and is coming from ‘book a demo’, that is, Calendly. 
• Next, create a task in Salesforce for this particular lead. For this, copy the action key and trigger the campaign. 
• If any new lead books a demo with inbound lead on the website then automatically a welcome message will be triggered. This task gets created in CRM against a particular lead. 

This is the basic lead creation flow.