Sometimes the support team may request a screenshot of what you can see on your side so that we can get a better understanding of your question. 

How do I capture the entire screen?
Press Shift-Command-3, then find the screenshot as a .png file on your desktop. 

How do I capture a selected portion of the screen?

Where can I locate this screenshot?
After you have captured your screenshot, find the screenshot as a .png file on your desktop.

How do I capture the entire mobile screen?
Press and hold the Power button on the right side and click the Home button at the exact same time. The screen will flash white and you'll hear the camera shutter sound (if your sound is enabled).

Where can I locate this screenshot?
This image will be saved in your camera roll. From here you have many options on how to send such as airdrop, email, SMS etc. 

How do I capture the entire mobile screen?
Press and hold the Power button on the right side and click volume 'Up' bottom on the left. The screen will flash white and you'll hear the camera shutter sound (if your sound is enabled).

Where can I locate this screenshot?
This image will be saved in your camera roll. From here you have many options on how to send such as airdrop, email, SMS etc. 

 How do I capture the entire screen?
Press and hold the Sleep/Wake (on/off) button on the top of your iPad. Quickly click the Home button at the bottom.

Where can I locate this screenshot?
Screenshots are saved to your camera roll along with your photos. On the later iOS versions, a 'Screenshots' folder will be created.

How do I capture the entire mobile screen?
Depending on which type of Android you have, to take a screenshot press and hold the home button and the power button at the same time OR press and hold the volume 'up' and the power button at the same time.

Where can I locate this screenshot?
You'll now be able to see the screenshot in the Gallery app, or in Samsung's built-in "My Files" file browser.

Thanks,

Customer Services Team.