Here you can learn how to install Google Plus Comments for your WordPress Blog. Just insert few codings to your WordPress Text Editor HTML Section your Google Plus Comments is ready to go live.
Here is the code. My suggestion is better you use this comment code for individual post rather than using for entire blog. Don't install any plugins for this. Sometimes plugins can be broken or there are some errors in sharing. So you can insert this code manually to every post or whichever post you want, it's your choice.
<div class="g-comments" data-href="Paste Your Post URL here" data-width="550" data-first_party_property="BLOGGER" data-view_type="FILTERED_POSTMOD"></div>
Don't adjust the width 550 pixels is the correct one for WordPress blog. If you need any help in this don't hesitate to post your query or help in the comment section.