Do you want to know where the RELAY is? Or the SWITCH?
The switch should be right near your side entrance door and is a spring return to center two position toggle switch. It should look just like the stairs switch, the awning switch, the porch light switch etc.
The relay is generally near your power center, behind/beside it. I suspect yours is under the bed.
Thor uses two different brands:
The RV Custom Products latching relay:
And the Intellitec latching relay: