To turn on the tail light of the Galaxy 24, first, make sure the battery switch is in the "ON" position:

At the handlebars, turn on the bike by pressing the ON/OFF power button:

The Galaxy 24 has a light sensor in the display panel.  The lights will come on automatically in low light situations.  If you would like to manually over-ride this feature, just press the Headlight button for 3 seconds.