You can use the 'PrintScreen' (may be labeled 'PrtScr') button if you are using a version Windows OS. Pressing the 'PrintScreen' button copies the entire screen to the clipboard. Pressing 'Alt' and 'PrintScreen' copies the currently selected window only to the clipboard.
Now you need to get the clipboard contents and save it to a file. You can use MicroSoft's
Paint application, just open it and use the paste function to get your image from the clipboard into
Paint. Depending on what you wish to show, you may want to crop the image - which is not exactly a built-in function of
Paint, but it can be done. Then select 'Save As...' from the file menu and choose JPEG as the format in the drop-down menu at the bottom of the save dialog box.
The above steps can be greatly streamlined by using third-party image software.
IrfanView is freeware and does most things people need to manage images.
Once you have a final image file, you need to put it on the web somewhere - such as a free image server like
PhotoBucket. Then just post the web address (
http://www.example.com/test_pic.jpg) of the image in your post and it should show up as an image.
That probably sounds more complicated than it is - but once you do it a few times, it'll be as easy as falling off a bike.
-Make7