This is for a Symantec certificate but should work the same with other certificates like Positive SSL issued by Comodo. Pay attention to the paths for certificate and CA chain files.

In Zpanel, instead of looking here c:/Program Files/apache/etc for help, maybe explore these paths:

c:/zpanel/configs/apache/httpd-vhosts.conf

c:/zpanel/bin/apache/OPENSSL-README.txt

c:/zpanel/fin/conf/openssl.cnf

A good question at this point is how to first prepare an SSL Certificate Request to be sent to the certificate authority (CA) so that a certificate can be issued to you by the CA.