I think you got the drift. Highlight the text and pictures, the right-click and select "copy".
Then start a new post. Instead of starting to type a new message in the body of the post, simply right-click and then select "paste". That should immediately pop everything you copied into the new post. You can then go through and make any necessary changes if so desired. Once you're satisfied, click on "post new message" (or whatever the heck it says), and lo & behold - a new post!
Note: Whatever you copy, will be there forever. You can "paste" the same thing over and over and over again, until you get tired of it. Then, if you copy something else, it simply replaces your previous "copy" with the new "copy". Your previous copy is now gone, and now, you have a new copy that you can "paste" to your heart's content. Lather, rinse, repeat. Not a big deal. You'll get the hang of it!