new Slider images not visible

Sorry I needed to add type of theme and site address- catch kathmandu and site is https://gatewayhotel.voltahotels.com again the problem is; I have successfully replaced featured slider images by creating posts and using set featured image but old images still show up when i visit the website

Only the new pictures are appearing for me. This sounds like a caching problem.

This tutorial should give you exactly what you are looking for:
I make changes, but nothing happens

Thanks but i found the problem. I needed to put ID number of the posts so it worked when I did