The valve and inlet hose can go anywhere between the tank and the pump. Just trace the water line back and see if you can find a convenient place to splice in the valve.
As was touched on above, you can also use air to blow the lines clear of water, but I'd be careful about using too small a compressor. The problem isn't pressure, it's volume of air you need. Generally a small compressor has a small, or no, reserve tank. To push the water out of the lines you're going to basically create a windstorm in the line. That means a wide open line with little restriction.
While a small compressor can blow out the majority of the water, you run a very real risk of leaving a bunch of drops behind, if there's enough of them and they can collect somewhere you could still have a burst line come spring.