First things first, you need to understand that the print screen button does work, but you need to have the MS Paint software in order to save the screen shot. This is because, the print screen button does take the picture, but you have to paste it somewhere in order to see what you captured and then save it.
Now, open the window which you want to copy and make sure that everything is in order.
Whenever you think it is the right time to take a picture of your screen, press the print screen button. The print screen button will give you a picture of the entire desktop. However, the Alt + Print Screen button is going to help you take a picture of only the window which you have opened.
Once you have done so, press the window button on your keyboard in order to access the Windows 8 application menu.
Type Paint in the search option so you can see the Paint Icon.
Click on the icon in order to open MS Paint on your computer.
Now you can either first click on edit and then paste the print screen; or you can right click and press paste. You can also use Ctrl + V in order to paste the screenshot.
Notice how everything which you could see in the window is now pasted in front of you. You can now save this file by going to file and then pressing save as. It is advised that you save the file in either a bitamp format or the .jpeg format. Both of them can be selected from the saving menu.