They have to be hosted online somewhere and then they get a URL... an address. Then you use that picture icon up to the left of the film strip looking icon (which is for vids I'm guessing). When you click that pic icon it will give you the option of uploading a pic from your computer as an attachment to your post. That's the easiest way. If the pic you want to post is already online you get the option of using the URL I mentioned.
