In general:
The Java keytool utility can be used to create a private key and then generate a certificate signing request (CSR) with the public key matching the private key. The CSR will then need to be communicated to a certificate authority (CA) for signing, at which point a certificate will be created. Once received, the certificate and the certificate trust chain for the CA must be imported into the keystore containing the private key.
To be more specific to your setup, you should open a support case, so the details about how you have it set up, versions,...etc can be shared privately, and we can give better answers.
