Essentially you'll need to configure your router to allow it to pass the video out onto the internet so you can view it from a remote computer. This is done through a process called port forwarding, however the exact way in which port forwarding is accomplished varies from router to router.
If you're unfamiliar with how to do that it's sometimes possible to contact the manufacturer of the router or your ISP to have them assist you with that configuration, however what's probably easiest for you is to have one of the techs from our sister site, techstring.com, configure your router for you through the internet. This is a quick process (it normally takes less than 30 minutes) and can save you a lot of stress for just $75.
If you were interested in using that service you can see all of the options and place your order at the following link:
http://www.techstring.com/product_p/dvr-router.htm