I have a Linux-based vendor-supplied virtual appliance that uses OpenSSL to manage certificates. The current server certificate is from Symantec so has to be replaced with a DigiCert. DigiCert is offering free replacements to existing customers using the same key pair - however, they are not accepting CSR's to do that. Instead, our DigiCert admin. is providing the replacement certificate as a Base64 .cer file.
All of the articles I have found talk about using a new CSR with the same keys but nothing about this specific case.
So how do I go about using OpenSSL to accept the new .cer file and associate it with the existing private key? I have all the relevant passwords/passphrases, etc.