AirTM API: How to Build a Form?

Hello,

I am somewhat new to APIs. I have integrated PayPal payments successfully. With PayPal, I can send the user to the payment page using an HTML form. Here is an example ...

<!-- PAYPAL -->
<form action="https://www.paypal.com/cgi-bin/webscr" method="POST" name="_cart">
    <input type="hidden" name="cmd" value="_cart" />
    <input type="hidden" name="upload" value="1" />
    <input type="hidden" name="no_shipping" value="1" />
    <input type="hidden" name="business" value="" />
    <input type="hidden" name="currency_code" value="USD" />
    <input type="hidden" name="item_name_1" value="" />
    <input type="hidden" name="amount_1" id="amount" value="1.00" />
    <input type="hidden" name="custom" value="" />
    <input type="hidden" name="return" value="" />
    <input type='hidden' name='notify_url' value="">
    <input type="hidden" name="cancel_return" value="" />
    <input type="submit" class="submit" value="Deposit Money Via PayPal">
</form>
<!-- PAYPAL -->

I want to do the same thing for AirTM. Here is their developer page: https://docs.airtm.com/purchases-payins/create-purchase

I am not sure where to include the Header information.

Can you help?