LDAP & Active Directory - step by step?

I just need some pointers. I have installed as per the website. When I log on I see the following: http://prntscr.com/7npgck

The LDAP button appears to be off. Therefore edited /etc/gitlab/gitlab.rb as follows:

gitlab_rails['ldap_enabled'] = true
gitlab_rails['ldap_servers'] = YAML.load <<-'EOS' # remember to close this block with 'EOS' below
  main: # 'main' is the GitLab 'provider ID' of this LDAP server
  label: 'LDAP'
  host: '192.168.100.2'
  port: 389
  uid: 'sAMAccountName'
  method: 'plain' # "tls" or "ssl" or "plain"
  bind_dn: 'cn=ldap-user,ou=College Users,dc=college,dc=school,dc=nz'
  password: 'pwd'
  active_directory: true
  allow_username_or_email_login: false
  block_auto_created_users: false
  base: 'ou=Staff,ou=College Users,dc=college,dc=school,dc=nz;ou=students,ou=CollegeUsers,dc=college,dc=school,dc=nz'
  user_filter: ''
EOS

My Questions are:

  1. Does the above look fine in principle?
  2. Do I need to install anything else on the Ubuntu server?
  3. How do I get the button next to LDAP (in the screenshot) to turn green?
  4. Am I missing some admin controls?

The LDAP block is very sensitive on leading spaces since it translates to yaml. I edited your code block above to use two spaces for identation. Can you try if it works?