Business Feature Theme: How to Show ALL Latest Posts

Is there a relatively easy way to have the Business Feature theme show the latest posts from all existing categories on the front page?

Right now you can only select one SINGLE category at a time. It would be much better to also have the option to show all "Latest posts in general" since my site has multiple categories, which are updated frequently.

Would it be easy to customize it even if I have to dig into the css editor?