RAH,
You can right click on an image hosted by Imgur and one of the choices in the menu will be to copy the image link. You can used that image link in two ways. One is from the full editor where you select the add image icon. When prompted just paste the link. One way is to type the tags and paste the image link between them.
e.g. [img] linkaddress [/img]
Give that a try. Hope it helps.