I don't know dameware so I don't know it's needs. You probably need a VPN in order to be able to access it via the internet. A free, easy to use VPN is hamachi. With it you will be able to map drives from a remote PC to yours and access them using the driveletter you assigned them.
Also very simple and probably a lot faster, as only the input/output actions (keyboard, mouse, display, sound etc) are transported across the internet and not the complete data, is to use logmein free. With that you will be have the remote PC's display on your PC and will be working directly on that PC. Both tools are from logmein:
http://logmein.com