In the benchpress workout the bar is initally resting on arms conected to a bench that you lay on. The arms are perpendicular to the bench. In order to execute the workout you lift the bar off the arms lower it to your chest and then fully extend your arms.

It is important to that your hands are equally distanced from the center of mass which is at the center of the bar, becuase the bar is symmetrical. Here is a picture of a benchpress.

Here is a diagram showing meaausrements and vectors of the bar.

Torque is angular force, that is realtive to the distance the force is from the hinge. In benchpress your hands can be considered a hinge that the bar could potentially rotate around. Torque is circular motion so if your hands rest in the middle of the mass the weight on one side would be positive, and the weight on the other side would be negative which would keep the sum of the torque at zero.