How can I take screenshots on both my computer and my mobile device?

You can capture a screenshot by following the steps below.

iOS
On the iPhone model with Face ID, you can capture a screenshot by simultaneously pushing the side button and the volume up button.If your iPhone has a home button, you can snap a screenshot by simultaneously pressing this button and the side/up button.
Android
To take a screenshot, tap the Power and Volume Down keys simultaneously.
Windows (computer)
With the Fn + Print Screen (PrtScn) Keys, you can grab a screenshot of the complete screen.
With Alt + Print Screen Keys, you can grab a screenshot of a single window.
The Win + Shift + S built-in Snip & Sketch tool can be used to capture screenshots.
OS X (Mac)
Shift, Command, and 3 Press and hold these three keys together, then you will see a thumbnail in the corner of your screen, click to edit the screenshot, then wait for the screenshot to be saved to your desktop.
*How to Capture a Section of a Screen Using Shift, Command, and 4 Hold down these three buttons and then drag the + symbol to select an area of the screen to capture. To move the selection, hold down the Space bar while dragging.

By clicking the attachment in the lower right corner of the chat screen, you can send the screenshot you took.