It is a little bit different from the well used IIP add-on. I dont test it on my page, but if I understand the system it should work like this:
Go to control panel, post islands. Create a new post island, give name and define the island type. Then you can select the forums whitch contains the news (multiple select with ctrl-click)
When submit it you have create a post island with your news forums and this can be pulled to the page with the generated code from portal setup.
There is no News Island by default, thats correct. Maybe Rick add a external link for the build in news system for the portal so we can pull it without creating an extra post island. The post island is a workaround but should do the job.