How does using Tidal energy affect the moon?
It is minute and inconsequential.  Without tidal energy harvesting, the motion of the water is ultimately converted into heat, it has a very small heating effect (that is swamped by the heating caused by the sun). With tidal energy harvesting, instead of heating the water, a little of the energy is converted to electricity (which is then converted into light or heat,  ultimately the energy becomes heat)
The tidal dams can change local tidal patterns, which could have a minute effect on the moon's motion, but this effect is minuscule.