Usually you have to take the top off and click a little switch. Some have settings to "high" or "low" or could be either "amber" or "white" the middle setting is usually off......

Hope that helps!

I've got an 18 pack that I bought at Sam's and the instructions said to put them in the sun for 3 solid days before turning the switch on in order to fully charge the batteries. Then, turn the switch on and they should be good from there.

And usually there is a strip of plastic between the battery and the unit that has to be pulled for contact between the metals.