1. Open an account at a free photo sharing site. I use photobucket.com.
2. Capture your screenshot using the "Print Screen" button in the upper right corner of your keyboard, then go to Paint (in the Accessories, for PC), paste the screen shot, and edit it down to the desired image. Be sure there is no personally identifying info in the image. Save it as a .jpg or other similar image file
3. Upload the image you want to use from your computer to this site. In the case of Photobucket, once you upload your image(s), you then select View Albums to see your image. Photobucket has a one-click option to copy the image, so you can then paste it in your message.
4. Now, return to FlyerTalk and click reply or start a new post. Type your post, then when you're ready to insert the image, click on the insert picture icon just above the post (it's on the same line as Bold, Italtics, Underline, etc.). Depending on your computer, you may get a yellow bar at the top of your screen asking if you want to temporarily disable scripts. Make that selection and try again.
5. Don't change any of the formatting on the line that pasted to your post or put any text before or after the pasted text on the same line.

When you save the post, you will then see your image.