To add a slider on Drupal 8, you can follow these steps:
1. Install and enable the Slider module in Drupal 8, which can be downloaded from drupal.org.
1. Create a new slider by going to Structure > Slider > Add slider. Give it a name and select the type of slider you want to create.
1. Add images or content to your slider by going to the Content tab and clicking on Add content. You can add multiple slides to your slider by repeating this step.
1. Configure the settings of your slider by going to the Settings tab. Here, you can customize the layout, animation, and other settings of your slider.
1. Add the slider to your Drupal 8 website by using the Views module. Create a new view and select the format as Slideshow. Then, select the slider you created earlier as the data source.
1. Save your view and add it to your Drupal 8 website’s page or block where you want to display the slider.