Codeigniter Shield two interfaces (for site and for admin)

Hi, guys. 

I trying to implement CI shield to my project, but it have very small documentation. 

My project have a website with login for clients and separate login for admin to his panel with different urls.
I wanna to use shield at this two interfaces, but i don't understand how i can load special config for each, for example: 

• For /admin – use /modules/admin/config/auth.php
  
• For /userlogin use /app/config/auth.php (default config)
  

These two interfaces will have a completely different view, but they can use the same users database just as different groups (for example, groups for accessing the admin panel - admin / manager, and groups for accessing the user login - client)