I watched your video. You just need to click on the magnet. When the magnet is in color (orange/white), snapping is turned on. Then you just need to perform an action and move your cursor towards what ever you have chosen to snap to. Your selection will snap when your cursor is in the correct location for the snapping method you have chosen (i.e, if you are snapping to a vertex, just move your cursor to vertex you want to snap to).
Shift + Tab will toggle snapping on and off.