css help needed!!

hi,, normally i dont ask for css help buuut i havent been able to figure out how to animate stuff on my page for a while ;(
vvv
whenever i write the css to animate stuff it doesn't work,, i was thinkin of a fade in transition and maybe float animation for the body ? if anyone can help me find a solution that would be rlly nice ty <3
(sorry if i used any incorrect/confusing terms for things im still v new to css!! (corrections are very encouraged))