A Utility App for my organisation

I need to create an app for the employees in my department. The app should have four sections on the homepage.
First is the collection of company guidelines/instructions (various documents in pdf format in one place)
second is the various templates/formats used by the employees (again in pdf format)
third is the collection of educational resources in images, pdf or video form
fourth is the forum with contact details of all employees pertaining to the department across the country so as to facilitate discussion and sharing

How do I go about it? Any good app builder website. Seeking suggestions/guidance.

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?