We use Slider Revolution, one of the most powerful plugins for creating slider, so we have included some demo slider in the theme.
To import slider, go to WordPress Dashboard > Slider Revolution, click on Import Slider and then a pop-up window will be open.
In the opened window, select your preferred slider file for a demo, then click on “Import Slider” and wait until the import is complete.
You may have an error from Slider Revolution while the slider is completely imported in Front-End. There is nothing to be worried about, go to the page Back-End and set Slider again.
Slider Revolution Documentation