There is indeed a link in your post, but it's a weird one. It's not an image link, but it rather appears to be the link to a Google search for images about watermelons. I have changed the image tags in the quotes here-above for the link you pasted by naked URL tags, so you can see for yourself that it's not an actual image link.
The way you get an image from such a search is that you must first right-click the image and then select
"View Image" from the browser's popup menu, and only after that can you right-click it again and choose
"Copy Link Location" from the menu. Google has recently changed the way that works because of so-called "privacy considerations" — read: copyright enforcement. :rolleyes:
That said, it is also always possible — although not applicable in this situation — that an external source doesn't allow the image to be shared. That happens sometimes. In fact, it is one of those annoying things that I always come across with articles posted at
The Guardian. I can never get their images to embed here at the forum, so I must then always hunt for an image that's not hosted on their site.
Now, apart from linking an image into your post from an external source on the web, you can also upload images from your own computer as attachments — see
this Q&A thread. ;)