How to add An input field located outside the HTML form (but still a part of the form)

Input Example.

index.html

Example: HTML

 <form action="/action_page.php" id="form1">
  First name: <input type="text" name="fname"><br>
  <input type="submit" value="Submit">
</form>

Last name: <input type="text" name="lname" form="form1">

Output should be:

Type:	html
Category:	Web Tutorial
Sub Category:	HTML Attribute
Uploaded by:	Admin