change the slide

@kaic: Thanks for your appreciation and 5 stars rating. For fast response please add your queries in our support forum at https://catchthemes.com/support-forum/forum/catch-kathmandu-public/

That is demo slider images. This free theme uses Featured Post Slider and Category slider to highlight your post. So, if you check our theme instruction page https://catchthemes.com/theme-instructions/catch-kathmandu/, it is described as below:

Featured Slider

Catch Kathmandu supports 2 different Featured Sliders to choose from 1. Featured Post Slider and 2. Featured Category Slider. But if you want to add either Featured Page Slider or an independent Featured Image Slider then you need to upgrade to Catch Kathmandu Pro Theme.

Featured Post Slider:
First you need to create a Post and then add Featured Image to the Post. Then you should remember your Post ID and follow these steps.

1. Go to “Appearance => Theme Options => Featured Slider” in your WordPress Dashboard
2. Under Slider Options select Slider Type as Featured Post Slider
3. Here you can also change the number of slides, slider effects and timing
4. Under Featured Post Slider Options, simply insert the ID numbers for Posts in the boxes, one Post ID number in each box
5. Save your changes

Note:
* When you add the Post IDs, make sure your posts have Featured Images
* If you are unable to find post IDs, please install Catch IDs Plugin to find the Post IDs

I have tried everything but your slider image can not changed.
i have installed theme from wordpress panel.
i have free version.

Did you follow the steps mentioned above. Maybe you might want to check this screencast https://catchthemes.com/blog/videos-blog/video-series-adding-featured-post-slider/

You need to:
1)Add new posts with some content (for info on image) and with featured image(required !!!).
2)Enter the ID’s of them into the Featured Slider settings (Appearance => Theme Options => Featured Slider)
3)Save and it’s Done!