If you performed a custom installation and did not install the LDAP driver on the Metadirectory server, you have two options:
Install the files on the Metadirectory server, using the instructions in Considerations for Installing Drivers with the Identity Manager Engine
in the NetIQ Identity Manager Setup Guide
Install the Remote Loader (required to run the driver on a non-Metadirectory server) and the driver files on a non-Metadirectory server where you want to run the driver. See Configuring the Remote Loader and Drivers in the NetIQ Identity Manager Setup Guide.