Understanding authentication and session management using Spring boot

I have made a spring boot project with mongo db as backend. I want to ensure that users are authenticated and authorized while maintaining some kind of in memory session (using redis or something in built in spring session)
I have been through lot of turorials like this, this, this etc

All of them ask you to extend WebSecurityConfigAdapter, configure HttpSecurity and provide a UserDetailService. Which I have done the following way.

@Configuration
@EnableGlobalMethodSecurity(prePostEnabled = true)
@Order(SecurityProperties.ACCESS_OVERRIDE_ORDER)
public class SecurityConfig extends WebSecurityConfigurerAdapter {

    @Bean
    public UserDetailsService userDetailsService(){
        return new StockUserDetailService();
    }

    @Override
    protected void configure(HttpSecurity http) throws Exception {
        http
                .authorizeRequests()
                .antMatchers("/login/**").permitAll()
                .antMatchers("/logout/**").permitAll()
                .antMatchers("/admin/**").hasAuthority("ADMIN")
                .antMatchers("/broker/**").hasAnyAuthority("BROKER")
                .anyRequest().fullyAuthenticated();
    }

    @Override
    public void configure(AuthenticationManagerBuilder auth) throws Exception {
        auth.userDetailsService(userDetailsService());
    }
}

But what I don't understand is where is the sessin management taking place and what is the url that the user should use to login? If I write a controller with mapping for /login, what should my action be inside the login controller. I really am not getting the whole picture.

UPDATE

I tried posting to /login. I get this error

{
"timestamp": 1494842451672,
"status": 403,
"error": "Forbidden",
"message": "Could not verify the provided CSRF token because your session was not found.",
"path": "/login"
}