Whichever method one choses to generate the certificates, there should be two files server.key and server.crt (which is either the certificate sent from the CA, or the self-signed certificate).
One may place the server.key and server.crt files into any directory, however, the directories usually are /usr/local/apache/conf/ssl.key and /usr/local/apache/conf/ssl.crt respectively.
To install the SSL Certificates into Apache, one simply needs to notify Apache to where the certificate key files can be found on the server.
Within /path/to/installed/apache/conf/httpd.conf (usually /usr/local/apache/conf/httpd.conf), simply search for these directives, uncomment them and edit the file locations (if need be):
SSLCertificateKeyFile /usr/local/apache/conf/ssl.key/server.key SSLCertificateFile /usr/local/apache/conf/ssl.crt/server.crt