If you have a picture you want for example from PotCO you can hit the button "Print Screen" on your keyboard. (Takes a-while to find). Then open up Paint or any picture editing program and hit Ctrl+P=Paste , your picture will be visible.
Time to crop it, depending on what program you are using it is different. Ill be using "Paint" a default program.
In Paint you will see a "SQUARE" icon on the top left. (dotted lines)
Click on it and DRAG from 1 corner to the opposite.
Do Ctrl+C and open a "NEW" document.
Ctrl+P and you will see your picture.
Save the picture and go to "tinypic.com" or "photobucket.com"
Upload your picture, and click on the picture (if your using tinypic) and click on either "Full screen" or "Open in a new window".
Copy the Link and upload it by clicking the "Tree" icon when you are posting a thread and paste the link