Setting up a project
Adding PowerUI to a project is as simple as dropping in the package then delete the example scenes folder. No further setup is necessary aside from running it at least once (so it can automatically setup itself).
Creating a new UI in a scene
GameObject menu > UI > PowerUI > Main UI
This will create a GameObject called main-ui in your scene (feel free to rename it). If you click on this GameObject, you'll see that it has a "Manager" component which you can then set your HTML content to. See the manager guide for more information on that.