Windows 2012 R2 Essential is a great product about small company up to 25 users.
Here they are more articles that talks about that more deeper inside this blog.
Today I would like to focalize that WSUS role is not supported on this product but, with Microsoft hotfix, and installing it as standard procedure you could create GPO and link pc to that.
Here they are more details and relative useful step by step article.
http://blogs.technet.com/b/sbs/archive/2013/06/25/how-to-install-wsus-3-0-sp2-on-windows-server-2012-essentials.aspx
Note: You will need to provide your email address and the hotfix download location will be emailed to you fromhotfix@microsoft.com.