How to set up SSL certificate (not self-signed) on virtual host on Ubuntu?

[Diablo925]

/ssl/folder/domain_cer.crt
<VirtualHost *:443>
ServerAdmin you email
ServerName domian
DocumentRoot /var/sentora/hostdata/username/public_html/domain/
SSLEngine on
SSLCertificateFile /ssl/folder/domain_cer.crt
SSLCertificateKeyFile /ssl/folder/domain_key.key
SSLCACertificateFile /ssl/folder/intermediate.crt
SSLProtocol all -SSLv2 -SSLv3
SSLHonorCipherOrder on
SSLCipherSuite "EECDH+ECDSA+AESGCM EECDH+aRSA+AESGCM EECDH+ECDSA+SHA384 EECDH+ECDSA+SHA256 EECDH+aRSA+SHA384 EECDH+aRSA+SHA256 EECDH+aRSA+RC4 EECDH EDH+aRSA RC4 !aNULL !eNULL !LOW !3DES !MD5 !EXP !PSK !SRP !DSS !RC4"
<Directory '/var/sentora/hostdata/username/public_html/domain/'>
Options +FollowSymLinks -Indexes
AllowOverride All
Require all granted
</Directory>
</VirtualHost>