I'd just check your manual on the receiver. IN the olden days there were switched and unswitched outlets.
But most Subs have a selector switch on it that goes power-auto-on. When you select Auto, the Sub will turn itself on as long as it's senses a signal. It will turn itself off and into standby mode after a slight delay. There is usually very minimal power draw in standby.
I just looked at the rear panel (below) and there is no place to plug in the Sub for power.
So you must have the wrong model or ?