The TRN4D1IND is a lantern with the option of using either 4D batteries or 1 6V. If you use 4Ds, you must use the plastic battery cartridge included with the light. To change the batteries, simply twist the head ring counterclockwise to loosen and the remove it, pull out the lamp assembly, then pull out the battery cartridge. Replace the 4D batteries in the cartridge in the orientation indicated on the catridge itself. Replace the cartridge, then replace the lamp assembly (it will only go in one way due to the guide tracks on the lamp assembly. If you are using a 6V battery, you must remove the battery cartride and store it somewhere for safe keeping, then insert a 6V battery in the orientation indicated on the light. Finally, replace the head ring and turn the light on.