How do I set-up remote network access?

[bellis1]

I would like to be able to access my computer that is at home (from work) and plugged into Cox Cable Modem and Airport Express. I do the reverse because the work network was set-up by someone who knows what they are doing. I would like to be able to connect by ssh through terminal and remote access. The problem is I have no idea how to get the IP address set-up? Right now the address is just the local address. Can someone give me a quick run through of how to set it up and what security I should use. Can I just check the network firewell boxes built into OS X. Any help would be appreciated I've been searching and searching for a simple tutorial but cannot find what I am looking for. My computers are not set-up as servers either. I'm looking to learn. Thanks.