How to put screen saver in iphone x?

There are no screen savers on iPhones, if you meant wallpapers howewer, Go to Settings->Wallpaper->Choose a new wallpaper

Hello Erik. I have a question about my iPhone 8 Plus wallpaper

I changed it to one of my photos and I want to know why the wallpaper doesn’t appear upon my touch. I have to tap the home button?