Sorry about the "Add Registration" button guys. The Impulse devs do know about it and are working to fix the problem.
You should be able to right-click in the white listbox area and go to "Add new Registration". That would be just like pressing the button. I've also heard other people state that the button is clickable, just not visible. I'm not sure about that as my version of Impulse has the button showing up. If you wanted to try clicking the non-visible button, you could start at the bottom left and work your way to the right.
Here's a picture of where the button is supposed to be:
