It is possible to make a form field required, where the Web user filling out the form must enter something in the form field in order to submit the form. The default setting for a form field is that it is optional and not required.
You can make the following form field widgets required – Textbox, Checkboxes and Paragraph text box.
Mark the Field as Required
Step 1: There are 2 steps to make a form field required. The first is the mark the field as required within its widget
To mark a form field as required, edit the form field widget and select the checkbox “Make Required” for Textbox and Paragraph or “This is a required field” for Checkboxes.
Step 2: Indicate to the Web user that the field is required by adding a visual cue of an asterisk.
Sitefinity does not automatically give a visual cue or indicator that a field is required, you need to add one to the Label field of the form field widget with in-line HTML.
To do so, copy the following code and paste it in the label field just before the text of the label.
<span style="color:red">*</span>
This will put a red asterisk and a space after the label.