The Edge Sense setup screen will also appear automatically when you squeeze the lower sides of your phone the first time.
After you've finished setting up Edge Sense, it works in Basic mode which, by default, allows you to launch the Camera app and take shots with a squeeze of your phone. See Taking camera shots using Edge Sense. If you want to assign another action or app to the squeeze gesture, see Changing the action to take when you squeeze the phone.
Edge Sense also has an Advanced mode that gives you two types of squeeze gestures: a short squeeze and a squeeze and hold. For details, see Enabling Advanced mode.