zoom out title and add image

I would like to try to rewrite the title of the presentation, so i write this code:

title: "Title too long for the slide "
author: "Me"
date: "23/10/2021"
css: slide.css

Ii tried to add css but it gives me this error:
File slide.css not found in resource path
Errore: pandoc document conversion failed with error 99

then i would like to add a picture but it gives me the same error

Is the slide.css file in the same directory as your rmd file?