You have probably installed a package that works on Zope level, you don't have to install anything in Plone and you don't have any Plone UI.
Go to ZMI -> acl_users and add an LDAP multiplugin from the top right menu
Final note: evaluate a switch to plone.app.ldap (not sure if is already Plone 5 compatible): it will give you Plone installation and Plone UI.
Thank you for the reply. That was very helpful. I tried to use phone.app.ldap but Plone 5 crashes. Using Products.PloneLDAP, I am able to authenticate but I find authenticated users do not have the navigation menu on the left. There is no navigation other than "Home".