csr-gen | Generates OpenSSL Certificate Signing Requests in node.js | TLS library

I have a website in GoDaddy (Apache) and an application in Amazon AWS (Apache Tomcat).

Website domain (apache): example.com

Application domain (apache tomcat): sub.example.com

I know how to install the certificate for example.com in GoDaddy, I use this application to generate the CSR and Private Key:

https://www.rapidsslonline.com/ssl-tools/csr-generator.php

I copy the CSR to request the certificate and finally install it fine using the private key.

I know how to install the certificate in tomcat for sub.example.com creating a keystore then requesting the signature using the csr of the keystore generated and finally downloading the certificate and installing it, that's easy.

But I have a problem, I can use only one solution : Install the website certificate or install the tomcat certificate, but not both. Why? Because the CSR generated by the generator is different of the generated by the keystore, and I need the private key (that the generator gives).

Then, that's the reason of my question, how can I create a keystore using an existing CSR file?

Well my idea is to create the keystore using that CSR file (maybe exists a parameter for keytool), then using it to generate a new certificate. After this I can install in Apache and tomcat, How can I do it?

Maybe another solution is how to get the Private Key of a keystore, it will works too.