Post form with name and password / Costum Attributes

Hello guys,
here is the html code:

<form action="" method="post">
    First name:<br>
    <input type="text" name="uname">
    <input type="text" name="pwd">
    <input type="submit" value="Submit">

i want to integrate in my webflow form on my site:

What and how must i fill the Costum Attributes / Custom attributes?

I will use the nice webflow form and i will not integrate this html code.

Thank you in advance for your help!