Set your camera and shoot
Select parameters 1
Find the multiple exposure options in your menu, and set the number of shots you want to merge (usually two). On a Canon, select On: Func/Ctrl and the Additive mode. On a Nikon, change the mode to On, and turn Autogain to Off.
Shoot your first image 2
You can now take your first shot, ensuring you expose and focus correctly. Feel free to work in manual, program or either of the semi-automatic modes. Once shot, you may see a semi-transparent overlay to help you compose your second image.
Take your second image 3
Line up your second image carefully, adjusting exposure settings if necessary, and making sure you refocus. You can now check your shot by pressing the image review button. Make several attempts at each shot, as the results will be different every time.