Hello, use
SSL certificates module in ISPmanager on user level, install cerficate and enable in the module or in WWW domain properties (for new ISPmanager 4.4.x).
Check SSL certificate in IE/Chrome, for Firefox you should add
RapidSSL CA to Apache configuration file into SSL VirtualHost
SSLCACertificateFile /var/www/httpd-cert/ca.crt
Code:
wget -O /var/www/httpd-cert/ca.crt "https://knowledge.rapidssl.com/library/VERISIGN/ALL_OTHER/RapidSSL%20Intermediate/RapidSSL_CA_bundle.pem" --no-check-certificate