Adjust padding/margins in blog posts

Hi guys, I’m very new to WordPress and CSS and am having a bit of trouble with the Bard theme…

I’m currently trying to add padding to blog posts so that the title and text are compressed more to the centre, but every time I add CSS, it affects the text of the main blog page too…is there any way to adjust JUST the text within blog posts?
I’ve been using just the basic

.post {
padding: 40px
}

but that affects the text across the entire site.

I also wanted to ask if there is a way to change the post titles to lowercase, as they are all currently upper? And to change the font for post titles using CSS rather than using a plug in such as Google Fonts?

Thanks so much in advance!!