Generate the private key

openssl genrsa -out domain.sihnon.net.key 1024

Generate the Certificate Signing Request

openssl req -new -key domain.sihnon.net.key -out domain.sihnon.net.csr

Send the CSR to cacert.org, and cat the result into domain.sihnon.net.pem.

Set up the server to use the .key and .pem files.