Google+ is a social networking platform provided by Google to share news, images and videos and to communicate with the peoples in all over the world. As you said how it helps on SEO then you can create your business page here and promote it via sharing its updates and news. that all.
Well, G+ is very good for SEO. It's still not so important for promotion as users mostly prefer facebook, however with its different options as keywords adding, etc, it's rather important for SEO!
Google plus business pages are now allowed. And search results are ranked in g+ s received. Therefore, I think it is a vital tool.