img src="image location URL" (but you have to put it all within angle brackets, which I can't show as an example because they will be interpreted as HTML!)
You should make it clear to those that don't know .. It is not okay to just copy and paste an image link into forums .. or anywhere else, unless the image is linked back to a host site of your own .. otherwise .. It is known as Hot-Linking or Band-width Theft!
Just Sayin
I imagine that you are right about that, however, an exception may be when hot-linking to an image on a U.S. government website (since we own it).
I understand the concern; but my best “records” here have been 500-600 hits, not a lot of bandwidth. A lot of my choices are from Flickr or Panoramio or government sites (like the Hawaii Volcano Observatory); those are essentially there to be seen. When I’ve posted from, as an example, a photographer’s site, I do give them the link back, and they might not mind the advertising if they’re commercial. But I could sign up for an Imageshack account and use that instead of the direct link.