$ sudo apt-get update
$ sudo apt-get install freeradius-ldap 

freeradius-ldap is installed in your system.

Make ensure the freeradius-ldap package were installed using the commands given below,

$ sudo dpkg-query -l | grep freeradius-ldap *

You will get with freeradius-ldap package name, version, architecture and description in a table

freeradius-ldap package basic information: