How do I insert the image into article?
If you have a wysiwyg option you can insert images into the body field.  There is a wysiwyg module that provides good integration and management and lets you use one of several engines.  If it is okay to have the image at the start or end of the body text, and not in the middle, then go to the Display Fields tab at the top of your screenshot and drag your image field into the appropriate order.  Also you can set image display size and other options from that area.