How do you post photos directly in Answers/Comments?

I know this might sound as a dumb question, but seriously how? I've seen some answers in which there were 4/5 photos between infos and other links
I've tried to copy-paste an image directly in the box (on Word that worked) but nothing
Then I've tried to copypaste the link itself, and "it was possible" but when I tried to reopen it the Link opened a "403 Forbidden" error page

Am I missing something? Do I need some kind of Converter or what?