Post form with name and password / Costum Attributes

Hello guys,
here is the html code:

<form action="http://logbook.pestscan.eu/PS_Web/APILogin.aspx?KOPI" method="post">
    First name:<br>
    <input type="text" name="uname">
    <br>
    Password:<br>
    <input type="text" name="pwd">
    <br><br>
    <input type="submit" value="Submit">
</form>

i want to integrate in my webflow form on my site:
https://preview.webflow.com/preview/schdok?preview=aec290360ad6c91dc369ad1bc0a57242

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!