folders in the dock

Drag it in to the dock.

When you do drag a folder to the Dock, it has to be to the right of the divider:

.

Once it is in the Dock, if you right-click or Control-click the folder icon you can change how it is displayed (as Folder or as Stack) and how its contents are displayed.

Please read the following two apple docs:

Mac 101: The Dock

Mac 101: Customize the Dock

Since this is kind of related to the original post. I'm having a similar problem with a macbook.

I have a 13" macbook from 2009 and for some reason can no longer change my desktop image by just clicking on an image in system prererences>I-Photo. Does anyone know what the problem could be? Also the I-photo application won't stay in my dock. I can drag it to the dock and it will stay while I'm using my mac but when I shut down and turn my mac on again, it's gone. I can still use the application, just can't keep it in the dock between uses. I have a feeling that both problems above are related. Can someone please help? Thanks

Your problem may not be exactly the same as that of the original poster of this old thread, and it can be very confusing for everybody if we try to answer more than one question in each thread.

In order for us to give your problem our undivided attention to try to solve it, would you kindly start your own thread, describing the trouble you are having in the fullest detail, including completing your details to show what Mac you are using, what operating system, and what version of the application in question. Please remember to post in the forum relevant to your hardware or version of OS X.