When you create a #Hostname #SiteCollection within SharePoint 2013 you will notice that the default user groups aren’t there. This is because they aren’t created when you use #PowerShell to create a hostname site collection.
To get these groups back, this can be done via PowerShell or simply doing the following:
Navigate to http://yoursitename/_layouts/15/permsetup.aspx
From this page you will see the following:
Simply click on OK and the groups will be available.
The important part of the URL is
Have fun with your permissions!