Using the tabs along the top, select Security. By clicking the small gear icon or Tools tab in the upper right corner of your window, you'll open up a drop down menu where you can select Internet Options.
This is done the same way on all versions all the way up to Explorer 10. If you've tried bringing up your cameras in Internet Explorer and have found yourself looking at a blank screen (not an error page), you've connected your DVR properly, you just need to enable the ActiveX plugin. If you want to save yourself some time, stick with Internet Explorer. In order to view your cameras on any computer, you need to initially enable all aspects of the ActiveX plugin and for now, Internet Explorer is the only browser that consistently allows for this in it's entirety. In most cases, you won't be able to use Chrome, Firefox, Safari, or any other privately owned browser such as these.
You'll first want to look at what internet browser you're using. Assuming you've connected your DVR/NVR to your network correctly, this is a pretty simple issue to fix. After installing your security camera system, one of the first walls you might find yourself running into is getting your camera feed pulled up on your internet browser.
