A video demonstration for this topic can be found in your website dashboard, under Video Tutorials > Yoast SEO Tutorials

  1. Login to Dashboard
  2. Go to SEO on the right-side menu
  3. Select Social on the sub menu
  4. Under Social, there are five tabs; Accounts, Facebook, Twitter, Pinterest and Google+
         Accounts - You can enter the social media URLs for your account on this tab to let search engines know which profiles are associated to your site. Click Save Changes
        
         Facebook - Unless you have another plugin that already outputs OpenGraph data for Facebook, leave the settings on this tab Enabled. This adds the meta data that Facebook, Pinterest needs  in order to share your titles and description and featured images whenever people share your post.
              Click Add Facebook Admin button to allow Yoast SEO plugin to retrieve your Facebook Admin's Name, which will be used as a reference, and Facebook User ID, to provide statistics about your website inside Facebook.
              Under Default Settings, you can specify default image used when the particular post or page does not contain any images.
              Click Save Changes

         Twitter - Twitter cards are the best way to share your articles in Twitter since it features a large image, title of your post or page, and goes beyond the limit of characters when posting in Twitter. Make sure that this feature is enabled. You can also select which Default Card to use; Summary or Summary with large image. Click Save Changes

         Pinterest - This also uses OpenGraph metadata to share your content, similar to Facebook. To use this, you need to make sure that the use of OpenGraph metadata is enabled under the Facebook tab. Then you need to verify your site with Pinterest by going to your Pinterest account and click on the hexagon icon. Then scroll down to Website and paste your website URL. This will provide you with a code that you need to copy and paste to Pinterest Confirmation box under Pinterest tab in SEO > Social menu in WordPress. Click Save Changes. Finally go back to your Pinterest account to complete the process.

        Google+ - To share your contents to your Google+ account, paste your Google+ Page link for your business on the Google Publisher Page box and click on Save Changes. Then go to your Google+ page and add a link to your website in order to complete the process.