Replace the contents of /var/opt/opscode/nginx/ca/www.yourdomain.com.crt
with your ssl combined certificate.
Make sure SSL certificate includes DigiCert ca root certificate
Replace the contents of /var/opt/opscode/nginx/ca/www.yourdomain.com.key
with your ssl key.
Reconfigure chef server
chef-server-ctl reconfigure
Restart nginx
chef-server-ctl restart nginx
Test your ssl certificates by going to a browser
https://www.yourdomain.com
Locally, you'll also need to run
knife ssl check
to test new SSL certificate and
knife ssl fetch
to pull down the new certificate to the trusted_certs
directory