With Photoshop CC, Koko, the stacking option is under the
Edit menu; but like so many PS features it isn't instantly obvious and there are several ways to achieve the same result. To begin the exercise, try with just two shots.
Very basically, this is what I do.
Open Raw images and adjust. Select All and open to main edit window. I use Bridge so I never bother with Lightroom. If you have a lot of images, or aren't working in Raw, or are working on pre saved images you may find
Load Scripts to be a better option for you. Or even copy and paste. Choosing your image import option is probably the most difficult bit of this procedure.
Anyway I now have my images on the main work screen with their names showing along the top
Toolbar. Click on
Windows in the top Toolbar and select
Arrange and tile all images vertically (or horizontally).
Right click the Background image and select
Layer from Background. This will turn your base image into a layer. Select all layers and go to the
Edit menu (top toolbar). Select
Auto Align Layers (check that Auto Projection is chosen in the pop up box).
In reality it is much easier to do than to describe how to do it.