Single sign-on (SSO) is a property of access control of multiple related, but independent software systems.
With this property a user logs in once and gains access to all systems without being prompted to log in again at each of them.
As different applications and resources support different authentication mechanisms, single sign-on must internally translate and store credentials for the different mechanisms, from the credential used for initial authentication.
The users have to be imported from LDAP or Active Directory
Go to Settings tab -> Advanced System Settings -> Global Settings
Change the setting value of the setting key “Single sign on setting for portal login” to 1
Remove the comment tags for the following content in Web.xml file below the line "<!-- NTLM Authentication Configuration -->"