To start using Hot Flash Mode, tap Modes from the main screen of the app. Tap on Hot Flash Mode (in the Cooling section) to set it as your default for all future cooling sessions, until or unless you decide to change it.
If you don't see Hot Flash Mode in your Modes menu, you may need to manually update your app. Find the Embr Wave app in the App Store (iOS devices) or Play Store (Android devices) and tap UPDATE. Hot Flash Mode was released with app version 1.5.1 in April 2020.