Sort:  

Actually it is very simple to implement! When you add a photo to post, it looks something like this:

![ADS_55.jpg](image address)

All you need to get clickable image is to change the format as following:
[![ADS_55.jpg](image address)](image address)

You add square brackets around original format and then copy image address in circle brackets and paste it after the enclosing square bracket.

That is simple, thanks! Next post I'll keep that in mind.