call category with PHP instead of "older posts"

Hello,

I am new to PHP and I am trying to customise my main page index file. Currently, the layout is to display a large featured image, followed by 4 featured images from the most recent posts, and then the next breakdown shows “older posts”

Instead I would like to call posts from a specific category and only display them. Does anyone know what code I will need to change/add to be able to do this?? You can find the code of my index.php file hosted below…

https://blog.attitudeclothing.co.uk/host/index.php.txt

and my blog can be viewed here: https://blog.attitudeclothing.co.uk/

Any help would be really appreciated.

Thanks x