OK. Are you aware how TLS in particular and PKi and asymmetric cryptography in general works?
If you want to just authenticate the other party (for example - want to make sure at your forwarder that the indexer you're connecting to is the one it claims to be), all you need on your forwarder is the certificate (just the certificate) of the CA used to issue the indexer's certificate.
But if you need to authenticate yourself as the forwarder to the indexer, you need both the certificate you got issued by the CA as well as your own private key. That's why it's called private key - it's something unique to you and you don't disclose it to any other parties. It's used to encrypt stuff during the communication so that other parties can decrypt it with your public key (included in the certificate).
For your own security, please, please, please get someone with TLS/PKI working experience involved and please read a bit about how it all works otherwise you can hurt yourself.
