This is a highly controversial training tool, mostly because misused by so many.

As I keep saying teach the basics using positive reinforcement and fine tune it with these tools.

Set it at a low level just to create a slight discomfort and right after giving the command tap the shock button every half a second, tap, tap, tap, until your dog executes the command. Mark and reward.
Quickly your dog will understand that that discomfort stops as soon as he complies and execute the command.