The best surveillance cameras are the IP based models, such as those by Panasonic. These cameras are plug and play--just them into any network jack. They do not require configuring. Plus, many of these cameras support pan/tilt and zoom so you can control them through the Orbiter.
If you have the regular analog cameras you will need to add a video capture board to your Core, and then attach the cameras to it. In that case, add the video capture board on the 'interface' page, and then add all the surveillance cameras on this page, specifying that they are 'controlled by' the video capture board.
There are also several settings for each camera. For save video, you can choose "All the time", meaning LinuxMCE will constantly record the video from the camera and save it on the Core. This can take up quite a bit of hard disk space, though. Normally you would choose "Only when motion is detected". This way LinuxMCE will only save the video when it detects there is movement, or something is changing. If you choose "Don't capture", then you will still be able to view the cameras live, but LinuxMCE will not keep an archive.
If you do want an archive, be sure to indicate how many days you want LinuxMCE to keep the archive. The default is 10, meaning LinuxMCE will erase any video archive that is more than 10 days old to free up space on the Core. If you are running out of disk space on the Core you can reduce this number so there is not so much space taken up with video archives.