Google can show how many Google+ followers your business has with your ads. These social extensions can appear with your ad without any setup if:
Your business has a Google+ page (you can create one using Google My Business)
Your Google+ page has a verified URL.
The domain of your Google+ page also matches the domain of your ad's landing page. This means you can link to different pages, but they should be part of the same website.
How social extensions work
AdWords ads that appear on Google and some search partners are eligible to show social extensions when our system can link them to an active and verified Google+ page. We’ll show the number of Google+ followers and +1s when it looks like they could improve campaign performance. Here's what they look like: