Added copy and paste icons as suggested in the video.
Then went to content, clicked article, then edit article. In Basic HTML, copy and paste buttons are available, but when some text is selected and copy is clicked, followed by paste, it is saying,
'because of the browser security setting, paste is not allowed, so use control + v for pasting it manually.
How to disable browser security setting in Firefox / Chrome, so that paste button will work directly?