This is amazingly simple!
Well, I say that, there is a small warning that comes with this. There is no official RSS feed for Google Plus. Any feeds made available cannot be relied on to last forever, either due to the third-party losing interest or money, or because Google release their own.
The first Google Plus Feed
The second Google Plus feed
However, some enterprising people have created plusfeed2. It really as simple as grabbing your Google Plus ID and appending it to the plusfeed2 url and putting it in an RSS widget. Just like any other blog.
Your Google Plus posts in you page content
If you don’t want to be restricted to your widgetized sidebars, you can insert your Google Plus posts directly into your posts using a shortcode:
NOTE: This way of adding Google+ posts relies on a third-party RSS feed, so it extends the embedding RSS feeds into your post content idea. Please make sure you have that short code working before trying it out. Alternatively, if you just want your Google+ posts in a sidebar widget, then you can use it normally.