You should begin with opening the Menu Trigger screen or Switch Task Trigger screen in Hi-Launcher Settings and selecting the Hard button press trigger.
Tap Select the button button to open the trigger configuration screen. You will be instructed to press a hard button. The button you press will become the trigger. Tap OK to save your selection, or press another hard button to change the setting again.
If the press-and-hold only checkbox is checked, the trigger will work only if you press and hold the selected button. This lets you maintain the button's default functionality if you press the button normally. On the other hand, if the checkbox is cleared, the button's default functionality will be completely replaced by Hi-Launcher's trigger system-wide.