On a shell:

openssl genrsa -out programmierung-dresden.de.key 2048
openssl req -new -key programmierung-dresden.de.key -out programmierung-dresden.de.csr

and a step by step guide on:

http://www.h-online.com/security/features/SSL-for-free-step-by-step-906862.html

https://www.startssl.com/

or a german version on my favorite hoster wiki:

https://wiki.uberspace.de/webserver:https

de_DEDeutsch