Automatic tasks on Lead Creation

Automatic tasks on Lead Creation

I am trying to setup CRM so that whenever a Lead is created a task is automatically created as well.
I have setup the Task Rule with the following due date:
WFRule Trigger Date plus 4 (I also tried with WFRule Trigger Date Plus 0)

But the help documentation does not tell me what will trigger this task creation.

Does anyone know how I can do this?