Select the category of posts which you want to display in the slider. (Featured images of the posts of the selected category will be displayed as slider images. Post Title will appear as Slider Title and Excerpt of the Post will appear on slider as slider description )
Featured images of posts should be at least 1920 px in width and 970px in the height for displaying slider images properly.
Use regenerate thumbnail plugin to crop all the images if you have already uploaded the Images.