You press print screen button. (prt sc)
Then you open pain or pain.net or similar program.
You select paste or press Ctrl and V to paste.
You "edit" the picture. I mean you erase "sensitive" data as how many diamonds or gold you have if you don't want to make it public, or any other type of information that you don't want to give us.
You save the picture at your hard drive. (usually jpeg type of file)
Then you visit a picture host site such as photobucket.com or any other you may know. (and create an account if you don't have already).
Finally you upload that picture to that site and they give you a link connected to that picture.
You copy that link and you paste it here at forum. like this(without the spaces inside []*:
[img ]here goes the link[/img ] all we see is the picture.
If you have any questions contact me again.
*that "option" is visible if you press the second icon from the second raw saying "Insert Image" right above this:
That inserts the [img ][/img ] and you will have to paste after ] and before [ your link in order to be visible.
If you are unable to do make the picture visible just give me the link as a reply here and I will edit your post to make it as it should. After that you press edit to see how the text is.