First: learn to use the command line, you'll need it.
Next: the CA, the certificate requests and the signing of said
requests is done with openssl.
You mac comes with openssl. So technically yoou have the tools needed.
BUT, if that sounded simple: it's not all that much in real life.
The parameters you need to pass to openssl to do what you need done
aren't all that trivial
for most mere humans (let alone for a "tecno analphabet").
The solution is to use the "easy-rsa" system that comes with a
distribution of openvpn:
it has a number of build scripts that do all of the creation of the
CS, the certificate
requests and the signing of the latter in a relatively easy to use way.
But even then it requires some familiarity with a text editor to get
your vars file set up
and some command line unix familiarity.
You'll find an openbsd source distribution at:
http://openvpn.net/index.php/open-source/downloads.html
(grab the source, it has the easy-rsa subdirectory in it - that's the
bit you need)
http://openvpn.net/index.php/open-source/documentation/howto.html#pki
has a step-by-step guide on using the build scripts.
caveat: never used a mac to do this myself, but I see little reason
why it would be different.
Success!