First of all your going to need the make and model of your DVR. The dvr system should have came with software but if not, then Google the make and model and download the software for it on your laptop. I have a Bunker Hill dvr camera system #61229 and I use Netviewer 2.0 and DVRClient Software. Once you set up your DVR Software your going to need to configure the DVR's ports through your internet service provider under PORT FORWARDING and last your going to need to probably adjust your Internet settings and firewall settings to allow communication to your DVR. Here are some helpful websites to get you started, good luck..
1. http/portforward.com/
2. http/www.networkwebcams.co.uk/blog/2007/10/22/howto-port-forwarding-101/
3. http/www.soleratec.com/support/rtsp/rtsp_listing
4. http/www.manualsonline.com/homepage/?n=1
5. http/www.cctvcamerapros.com/PTZ-Security-Cameras-s/45.htm