Wrap Around Images

Ok, I read https://codex.www.ads-software.com/Wrapping_Text_Around_Images
but I have some questions. When they glibly say “add the following to your style sheet”, does it matter where?
Instead of banging my head against the wall figuring all this out, is there a nice wordpresss style sheet out there that I replace the shitty one it came with? Thank you.