Windows key + printScreen key on Windows, ctrl + shift + 4 on Mac, dunno on Chromebook, depends on what’s been installed on Linux. That’s how you create a screenshot.
If you mean how do you copy code into for example the forum, move your mouse over it, select the text you want to copy, press ctrl/CMD + c (or go to file > copy, or right click and select “copy”). In the place you want to paste it, press ctrl/CMD + v (or go to file > paste, or right click and select “paste”)
When you enter a code block into a forum post, please precede it with a separate line of three backticks and follow it with a separate line of three backticks to make it easier to read.
You can also use the “preformatted text” tool in the editor (</>) to add backticks around text.
See this post to find the backtick on your keyboard.
Note: Backticks (`) are not single quotes (’).