Login to org using your credentials.
Click on Setup(Gear Icon).
In Quick Find Box, Type Flow. Select Flows under Process Automation.
Click on “New Flow” Button in order to create a Flow.
Choose “Record-Triggered Flow” and Click Next.
Choose Freeform as Layout option.
Select the Object on which flow is to be written and also the condition for triggering the flow as per requirement.
Set Entry Condition as per requirement.
Choose Actions and Relate Records options under Optimize the Flow Option.
Choose Create Records option under Elements section in Toolbox and it choose Object as SMS Message and set it’s Record fields as following:-
Lead__c->Record Id
RecordTpeId->Enter the Record Type Id
Customer’s Phone-> Phone field on Object Record.
Message Type-> SMS
Text Message->Enter the Text Message
User First Name->User First Name
User Last Name-> User Last Name
User Phone-> User Phone
The final Connected flow will be as following:-
After completing the flow, Save the flow and Activate it.