Hello,

Step 1. Go to Dashboard >> niwas-resort-hotel-pro Slider
Step 2. Click on Add New button
Step 3. Add the slider Name.
Step 4. Add the featured image as a slider.
Step 5. Click on ‘Publish’ button at top right of page.

you may follow our theme documentation for that, please check below link
https://luzuk.com/demo/niwas-resort-hotel/documentation

Thank You