@rsw 

Do you have a picture of the switch wiring before making changes?

Thanks for responding. I didn’t take a photo. I tried to replace a simple single pole switch. There are only three wires 1black(hot) , the neutral white wire and a ground and there really isn’t much choice where the wires attach on a single pole switch. Since I couldn’t get the smart switch to work I reinstalled the old fashioned single pole switch. I could take a photo of that if you think it might help. @rsw 

@rsw 

A neutral is never connected to a dumb switch.

The white in your case is a line/load and should of been marked black with black tape or marker.

I think I understand. When I checked for power on the two lines coming into the box, the line from the circuit breaker showed power and the second line takes the power to the light and so has power when the switch is in the on position.  Is that right?  So I should connect the two black lines from the switch to each of the two lines coming into the box.  What do I do with the white line from the smart switch?

@rsw 

The white from the switch needs to be connected to a neutral.

If you have other wires in the box, and one of them is a neutral, then connect that to the white of the switch.

Sometimes you will find a group of white wires under a wirenut in the box, that would be your neutral.

@B.Will 

Works!  Thanks so much. 

@rsw 

Your welcome.

Glad to be of help.