How to make subpoena required when trying to send?

Question

Angular

jsfiddle.net/HB7LU/27818
How to make subpoena required when trying to submit?

Answer 1

<p ng-show="myForm.username.$dirty && myForm.username.$error.required">Username is required.</p>

input.ng-dirty.ng-invalid{
  border: 3px solid red;
}