There should be a PrtSc or Print Screen button somewhere on your keyboard. Pressing it will copy a picture of the screen.
So, press it, load up MS Paint, and press Ctrl+V. That should paste the picture into Paint.
Save the picture somewhere on your computer.
Then, go to a website like
http://imageshack.us/, click browse, choose your picture, and click upload.
When it's done uploading, copy the direct link to the image, and paste it here.