How do I log different sets with Apple Watch?

Logging Different sets with Apple Watch is super simple. Just Force Touch (press the screen with a bit of force) the exercise's screen, then tap Log Different Sets. When you're done, tap Save.

If you do this frequently, you can change the interface of the Watch app to always have a button to quickly Log Different Sets. To do that, open SmartGym on the iPhone, tap More, then tap Apple Watch Advanced Interface. Choose the Log Sets Button. You only need to do this once. After that, SmartGym will remember your option.