Have you learned port forwarding?
http://qrcctv.co.uk/cctv/cctv-port-forward
By the sound of it this DVR (along with many DVRs) need active X and therefore can only be viewed from Internet Explorer!
Not much you can do about that apart from buying a DVR that is compatible with all browsers.
But you might be able to view it from mobile phones. You just need to download a compatible CCTV app.
Android CCTV App
http://qrcctv.co.uk/cctv/cctv-android-phone
Iphone CCTV App
http://qrcctv.co.uk/cctv/cctv-iphone
These apps are free of charge and work with many DVRs.