That's ok fella, just because you don't spend every minute on Internet forums doesn't mean you have to apologise for not following/understanding normal forum operating procedures.
It's cool, you'll get the hang of it in no time.
Anyway, yes, PM is short for Private Message, which is what it suggests, a message hidden from the public boards and other members. It's the best way to do private business and ask direct questions.
Correct, CS is an active member, spend not too long looking at the boards and you'll see his name, you can then click that and it will give you further options, one of which will be to send a PM.
I don't know for a fact about this one but most forums have a members list, I'd expect this place to have one TBH (to be honest), have a snoop around for it and locate CS.
You'll be creating your own memes in no time !!!