I've been looking this for a long time and cant find any tutorial or answer how can this be done, so i am hoping, someone here will be able to help me.

How can i add play icon to every image in video category like it is done here
demo.joomshaper.com/joomla25/news_iii/index.php/video

Hope someone will be able to help me

Hi. You need to be familiar with CSS to do this.