When using a TENS unit for nerve damage, do you use it on the spine or where symptoms are occurring

Factual Questions
1

Lets say you have nerve damage in your spine, but it is causing symptoms in your hands or feet. If you use a TENS unit, do you apply the pads to your hands or feet, or do you apply them to your spine where the nerves in your hands and feet are based?

2

Here is a chart:

3

Thanks !