Screenshot on Chromebook

Step 1:

Press Ctrl + Show windows at the same time (everything on-screen will be in your screenshot).

Step 2:

When the notification appears, click to see your screenshot, or find it in your Files app.

Step 3:

Copy to Clipboard, once you copy to the clipboard you can paste the screenshot in any email. 

If you need to locate older screenshots, you can do so by clicking the circular button in the bottom-left corner of your screen, selecting the up-carrot button, and then clicking "Files."

Step 1

Click on the app launcher icon in the bottom left corner (looks like a little circle).

Step 2: 

Find the Files app and click on it.

Step 3: 

The Files app is sorted by Recent, media type (Audio, Images, Videos), Downloads, Play files, and Google Drive. Click on Downloads.

Step 4:

You can view and delete any old or recent screenshots.