The tube runs up to the top above the waterline then to something thats called a mazzi injector, yours may have the new Bohls injector which is a little different but basically does the same thing.
As far as doing anything it will just come on and shut off by itself. Whether it is working or not hard to say. You will have to put your hand on it and see if you can feel it humming. Every time you turn a main pump on it will shut off untill that pump shuts off then it will turn itself back on, unless its in a filter cycle then it will operate as normal. If your spa has the highflow circ pump which it probably does then you dont really need a filter cycle??
Did you get a manual with it??? If not you can probably get one on line.