You can create custom messages that users will see on the sign in and sign out pages. For more information, see "Customizing user messages on your instance."
Configuring built-in authentication
-  From an administrative account on GitHub Enterprise Server, in the upper-right corner of any page, click .  
-  If you're not already on the "Site admin" page, in the upper-left corner, click Site admin.  
-  In the left sidebar, click Management Console.  
-  In the left sidebar, click Authentication.  
-  Select Built in authentication.  
Two-factor authentication
When using LDAP or built-in authentication, two-factor authentication is supported. Organization administrators can require members to have two-factor authentication enabled.
Creating your account
Once your instance has been created, you'll need to create your own admin account.
- On the "Create Admin Account" page at http(s)://[hostname]/join, choose your username, password, and email address, then click Create an account. 
- Sign in to your GitHub Enterprise Server instance at http(s)://HOSTNAME/login.
Inviting users
-  From an administrative account on GitHub Enterprise Server, in the upper-right corner of any page, click .  
-  If you're not already on the "Site admin" page, in the upper-left corner, click Site admin.  
-  In the left sidebar, click Invite user.  
-  Type the username and email address for each of the user accounts that you'd like to create, then click Generate a password reset link.  
Tip: If email for notifications is configured on the appliance, an invite will also be sent to the provided email address.