using wordpress in an already made layout/site..?

Hi, I’m sorry, but I’m completely lost as to how I can make the content on my index.php page to show up as the posts on my wordpress. I can get it to show the wordpress blog page as the front page, but I want my own layout to simply have the blog part.?
The site’s for things other than wordpress; I want to use that merely for news and updates.

This is probably a really simple question which was horribly asked. Sorry.