The headlight of Loomo is off by default and you can open it on the Loomo App.
With your app connected to the robot, step on Loomo to activate riding mode. And you will see the interface below. Now you can tap On to open the headlight. If you choose Auto, whether the headlight is on depends the brightness of the current environment.
Please note that you are only able to alter the settings of headlight when Loomo is on riding mode.