The“clicker”mechanism works by spring tension inside the torque wrench. The tighter the spring, the more twisting force (torque) it takes to make it click. When you turn the adjusting knob/dial on the end of the handle, that tightens the spring.
Set it to the lowest setting that you can, the closer to zero, the better. Letting it sit for a long time with tension on the spring will mess up the calibration because the spring will start to “relax” and will cause the wrench to start “clicking” earlier than it should, giving you false readings.
When using it, you should apply torque slowly and evenly, when it clicks, let off a little and then reapply tension - make it click more than once.