The main documentation is here. This is a summary. It is intended to help you get a service up using OpenLDAPfor authentication as quickly and simply as possible. 

For simple user auth add this to main ejabberd.yml:

host_config:
  xmpp.example.org:
    auth_method: [ldap]
    ldap_servers:
      - 127.0.0.1 #IP or hostname of OpenLDAP server
    ldap_port: 389
    ldap_uids:
      - uid
    ldap_rootdn: "uid=ldap_readonly,ou=people,dc=example,dc=org"
    ldap_password: "secret"
    ldap_base: "ou=people,dc=example,dc=org"

The ldap_rootdn should be a special administratiive user entry set up in OpenLDAP for ejabberd to use. “dc=example,dc=com” should be set to the rootDN of the directory. The password (unfortunately) has to be in “plaintext” so your config has to be well protected. 

vCard from LDAP

This is theoretically possible, see the documentation. This is not worth pursuing until after your ejabberd server is running and the LDAP connection has been well tested. Best explored on a non-PROD server.

Shared roster groups from LDAP

Theoretically possible, see the documentation.

Same comments as vCard.