Torque from Shear Stress Integration

Hello,

I have been working on a model of a flat plate very near the wall of a duct with air flowing through it.
In order to find the forces acting on this plate, I have been integrating T_stress over the surfaces of the plate.
Now, I would like to find torque acting on the plate and am struggling to figure out the function I need to integrate.
I understand that I need to multiply the result of the surface integration of T_stress by the distance to some axis to all points on the surface of interest, but I am not sure how to do this.
Any help would be greatly appreciated.

Thanks.