Welcome to the site !!
Can you post a picture of what "plug" your talking about ??
To post a image you need a hosting site like Photobucket , you upload your pic to it , then go to the picture and get the link on the right side (if your using Photobucket) , usually the "IMG" link will work , it will look like this when you "Paste" it into your post
But when done right and you submit the post it will show up like the image below