To take a screenshot in Windows, there are a few ways:
1: You can press the Printscreen button then paste the screenshot into an email.
2: You can hold the Alt key and press Printscreen, which will take a screenshot of only the current program that you can then paste into an email.
3: You can press Windows-Shift-S which will allow you to draw a box around a part of your screen and paste it into an email.
Please note that on some keyboards it may be required to hold the Fn or Function key before the Printscreen button works.
To add the picture to the forum post, you'll need to first click the "Switch to full Reply Screen" button. Then click on the File Manager in the Post Options.