PC:

Run the game and press the Print Screen (PrtScr) button on your keyboard --> stop the program.
Click on Start --> Programs --> Accessories --> Paint --> When the program opens, please press together Ctrl button + V on your keyboard or right click anywhere in the space of the program and select Paste.  You will see the screenshot you just took. Please save it on your hard drive and attach to your reply.

Mac: 

Hold down the shift and command keys down simultaneously, and then press the 4 key. Your cursor will turn into crosshairs, which you can move to the top left corner of the area you want to start your screen capture. Then press the mouse button down and drag it to the bottom right corner of what you want to capture. Release the mouse button.

You should hear a camera shutter sound, and the screenshot you've just taken will be on your desktop in a file with the name "Picture-1" (or a higher number if you have taken more than one screenshot). Please attach the screenshot to your reply.

iOS:

To take a screenshot, please do the following: click the Power button, and while holding it down, click the Home button --> You’ll see the screen ‘flash’ white and hear a camera ‘clicking’ sound. Now open the Photos app --> You’ll see the screenshot you just took as a thumbnail. Tap that photo to view the screenshot. Please attach it to your reply.

Android:

To take a screenshot, please do the following: press the Volume Down (or Home) and Power buttons at the same time, hold them for a few seconds, and your device will take a screenshot. Please attach it to the reply.