It can be tricky, if I am understanding what you are asking correctly. Here is what I do when I want to copy an image and post it in a thread.
I touch the image until I get the copy menu. I select copy image. Then I open a new browser tab, touch and hold until I have the option to paste. It puts the whole URL to the image there. Then I select all and copy the URL. Then I can paste it in a post/thread and add the image tags.
Hope that helps! Maybe someone knows an easier way to do it, but that is what I have found that works.