Download the ApplyHTTPS.zip script from the article linked below:
Unzip the file and select Run As Administrator from command line. ApplyHTTPS.exe can be used to apply an LDAP cert to NFA. It is a command line tool and must be run using administrator privileges.
When run, you'll choose the 3rd option to import the LDAP cert and then provide the full path to the .CER or .PEM file:
After entering the required information and following the instructions provided, the LDAP cert should be installed. Please test that you can authenticate via LDAP.