The purpose of "Fogging " the engine is to provide lubrication to your cylinders to prevent rust from building up over the winter as well as your intake manifold, heads and valves. Fuel stabilizer is used to keep your fuel from going bad. It has a shelf life, the octane rating goes down as the fuel ages, as well as "Gum up" or "Varnish" which may cause floats or needle and seat assys. ect. to stick or clog.
The other thing to consider, especially if your boat is outside, is the condensation that forms from the metal (Engine,oil pan, aluminum fuel tank ect.) constantly changing temperature. This is why some people recommend topping off your fuel tank prior to storage. Water can also form inside your engine and end up in your oil if you have a 4 stroke.
To fog your engine what you need to do is remove the air filter and find the throttle body, or carb, and spray the fogging oil directly in the opening. To help you find it, once you removed the air filter, look for the throttle plate, you can start the engine without the filter on and listen or feel (watch out for moving parts) where the air is being drawn in. Another method would be to remove the air filter, and with the engine off, have someone operate the throttle, you`ll see the throttle plate opening and closing as the throttle is moved.
When I had an outboard I did the same as ffishman
, I ran the engine for a while with the fuel stabilizer already added, shut it down, removed the spark plugs and shot the fogging spray thru the openings I then turned the engine over a few times by hand. It`s pretty easy to turn with all the spark plugs removed.