Is the webcam USB? Would expect that it is USB but wish to be sure.
What the guy at Best Buy probably did is just use a USB to micro USB adapter to physically connect the webcam. And hoped for "Plug & Play".....
However, the pinouts ( physical wired connections) between the webcam and Galaxy Tablet must be compatible. One or the other, or both, could be proprietary.
Plus the Galaxy Tablet would need to have the corresponding webcam drivers installed so the Galaxy and webcam could communicate and the results of that communication would be viewable. So some video and perhaps audio code would be part of the drivers. As well as some User Interface to configure and manage the camera.
USB is limited to about 15 feet so any long distance camera to Galaxy Tablet connection would be limited to that distance.
As for next step a wireless webcam may be viable. Or Bluetooth perhaps.
Here is a link that may help you get started:
https://www.verizonwireless.com/support/samsung-galaxy-tab-4-10-wifi-and-bluetooth-video/
If you have a wireless network at home then a wireless webcam that can join that network would be needed.