Blog headings & images

Hello, when I open my blog page (before I open a single post), the headings of my blog titles are not the style I want, how can I change that? Which heading number corresponds with the blog post titles?

Also, how can I make sure that the images I use inside my posts are the ones displaying on the main blog page?

And, if I want to add a blog feed on my home page at the bottom, do I need to add some kind of a widget?

thanks for the help