on a standard keyboard look above the number pad for a button that says PrintScreen/SysRq.
Have the image on your screen and hit Print Screen (make sure to move the mouse out of the way first)
Then open up Paint in your Accessories in Windows. Then hit "Paste" and the image appears in paint.
Then do Save As and make sure it is a jpeg.
Then go to tinyurl.com
It will have a BRowse button to upload an image, hit the Browse button and click on the file you just saved as a jpeg. It will upload the file and provide you a URL link.
Copy and paste the URL into the message screen here and then post. It will put the image in your message and you can put text above or below it.