Latest post from category with author image (widget)

I’m developing a online newspaper, and i’d like the layout to be similar to https://nyaaffarer.se/ and https://dagensarena.se/. But there’s one function i can’t figure out.

In their headers the show an authors image and the recent posts from a specific category. I guess they perform this using a PHP-widget – but how do i use the code?

Google couldn’t figure this out – i hope you can ??

Cheers!