Apurba Debnath you need to go to the original link of image like going on image link then deep press on that picture and open in new tab and copy the url from their if problem continue then download the image and host it over any image hosting website like dropbox, imgur and then paste the uploaded link in the src tag.
here is an code which can help in upload the image
here is an code which can help in upload the image and host that
and for upload on imgur you can follow this link
then paste the uploaded link in src