To create a topology in IOU you define how devices connect to each other via a NETMAP file. If you want more details on how to build a NETMAP file you can head over to Google and search for it.
Here's a diagram I did up for this topology, Note that the addressing is my own and that you are free to use anything you configure yourself. Since I'm not providing any base device configs you are on your own here.
2:0/0@server 3:0/0@server 4:0/0@server
If you like this and use it let me know. I'd love to hear about it.
If you liked this topology see my IOU topology #2