Building a customised Create User web page to initiate creation of new user in AD

Complete newb to AR and would like to understand the steps needed to be able to provide a customised web page to HR for requesting creation of a new user in AD.

I think the part I'm mainly missing is how to build a customised web form and present to HR users - as delegated admins - that captures the necessary initial user data and then initiates an associated workflow in which I can built all the data transformation and approval steps.

I'm using 7.3 on W2K16 server.

Many thanks,