OpenSSL/CSR question



I am trying to generate a CSR to secure my server.
However, when running the openssl command it complaints
that it can not find a directory.

The command I am running is the following:
openssl genrsa -des3 -out /home/yourdomain/ 1024

(though with my domain name). Am I supposed to make a
new directory first in the home directory and then run the command?

Also, If I am securing a subdomain. Should I use that
domain name, or is it always the “original” domain name?

Kind Regards!