Posts in separate boxes

by default your index.php should already place your posts into separate divs.. it’ll just come down to your css styling to make them ‘look’ more like separate boxes

start by looking into the code of the default theme Twenty Eleven, for instance.

or generally, check https://codex.www.ads-software.com/Theme_Development
(not sure is that contains showing post divs in the loop (?))

Thanks for the help, I managed to figure it out as said to look into the css.