All routers being different, basically its just in port forwarding part of the menu for the router. I have only done this on a couple of brands (Net Gear is the one I'm on now) and it just asks for a range of ports and an IP address, not the kind of port?. It on the firewall of your AV that you want to open (or exclude from the FW) the port -- if there is a choice exclude all for the default 52199 if you haven't changed that. It might say allow all or trusted or home office too maybe.
On the office side that's different of course -- you'd be getting in from the external fixed IP via the 52199 port and forwarded to the local IP (fixed normally through DHCP of the router if not Windows - most modern routers can assign a static IP now via the DHCP menu or at least give it a long term lease associated to a MAC address -- it works for me at least). The problem lots of people have is that their office has elaborate firewalls, and/or proxy access to internet -- but that's beyond the scope of most common mortals and best ask the IT department.
Did you read the article linked in the footnote to the WIKI one ? In it there a few links to check to see if you can connect externally before you actually leave your house.
http://yabb.jriver.com/interact/index.php?topic=60252.0