openssl req -nodes -newkey rsa:2048 -nodes -keyout privateKey.key -out CertRequest.csr -subj "/CN=mydomain.com"
openssl req -x509 -sha256 -nodes -days 365 -newkey rsa:2048 -keyout privateKey.key -out certificate.crt
I use Namecheap.com as a registrar, and they resale SSL Certs from a number of other companies, including Comodo.
These are the steps I went through to set up an SSL cert.