The RaspberryPi.org has a overview of how to install the OS onto your SD card, here:
There is a very good OpenVPN tutorial written by Lauren Orsini. She has also written a few other articles of things to do with your Raspberry Pi. Our OpenVPN tutorial is largely based upon her articles, with ideas added to improve security and tweaks that we found necessary to get things running, connecting and routing properly.
Building a Raspberry Pi VPN, Part 1:
Building a Raspberry Pi VPN, Part 2:
Lauren also has a good starting place for the server.conf file hosted on GitHub:
And the make script to assemble the client file(s):
I'll continue to add helpful webpages as I note them.