Infra8 Request Submission Designer

hello

We have just installed Infra V8 and I am in the process of creating a new form for a Workflow in the Request Submission designer. When I create a new Workflow and go to Request Submission designer screen it comes up with a default screen. Is there any way of actually using an existing form and just adding to that. I am trying to add extra fields to the standard Request Form (Inrequestdetails.htm file). Can someone please point me to the right direction as to how to use an existing form within the Request Submission designer.

Thankyou very much.