You can find these settings at your slide editor. You can reach the slide editor when you click on a slide.
Looking for the option to add a background image, color or video? Check out the documentation on the Slide settings's Background tab.
Do you need to add custom Background animation or Ken Burns effect for the slide? Look at the Slide settings -> Animation tab.
Would you like to rename the slide, set specific autoplay duration, change the thumbnail or set a link to the slide? Look at the Slide settings -> Settings tab.
Are you interested in the helpful Hotkeys? You can find a full list of them.