I have joined two lists. That part I get. What I don't get is how to add items to the subview of the combined list I've created. I have two lists that interact with each other. They each have a common field (Req. Number). The two lists are Requisition and Person. A user can submit multiple people to one Req. Number. When I created a linked Data Source between the two lists and then create a Data View from that source, I don't know how to make it so a person can submit multiple people for each requisition number (a many to one relationship). I've done a lot of searching and it seems that no one is posting this sort of thing. They all either deal with SP 2007 or end after joining the two lists.
Joining 2 lists is usually done through a Lookup column. I am not totally clear on your requirement but you could have a lookup column on your Requisition list that links to the People list. If this is the case then you would need to make sure this column is set to accept multiple values. The other option is to have a Lookup column on your People list that points to a Requisition - so when you add a new person then you select which Requisition they relate to.
The first option seems most logical but it does depend on your specific needs.