Enable slider

1- Go to Appearance – Theme Options
2- Select Slider settings tab
3- Check Enable slider
4-: Optional: Check Show slider on homepage ONLY if necessary
5- Click Save Settings

Add slider image

1- Go to Slider – Add New
2- Insert Title, description and URL
3- Click Set featured image to insert a slider image
5- Click Publish

Slider image size is 1080px (width) and 420px (height).
To add the next slider image, kindly repeat the above steps.