I have updated NivoSlider extension this weekend to support edit/re-upload functionality which can be helpful if you maintain large number of images and sometimes need to make changes. Below is a short screencast that demonstrates installing NivoSlider, adding it to the post and adding new image to the slider. It is about 3.5 minutes long with no audio, I used captions instead as explaining amount is minimum. I've just started learning video editing, so quality is not great but I hope it will help someone having questions on how to install and run NivoSlider.
One thing I forgot to mention about is that, when slider first time added to the post, you might need to refresh browser cache for it to show up on the blog. So if you add NivoSlider and see white rectangle instead of picture, hit Ctrl+F5 couple times to refresh the page.