Hello Marlinda,

Here is Complete step by step theme documentation. You may follow it for slider set up.
https://www.luzuk.com/demo/supermarket-ecommerce/documentation/

For slider set up, You have to follow below steps
Step 1. Go to Dashboard >> Slider
Step 2. Click on Add New button
Step 3. a Add slider name.
Step 3. b Add slider content.
Step 3. c Add the featured image as a slider.
Step 3. d Select Slider button link to product category & add button text.

Thank You.