Minimal-grid help with CSS

Can anyone please guide med to the right css for two problems I have not been able to solve.
1) I would like a border (1px black) around the single-post featured/main picture.
2) The capture for the picture is not quite in center of the picture. Can that be resolved with some padding somewhere?

An example page:
https://www.bundu.no/2019/05/27/norge-bidrar-i-en-fn-operasjon-i-mali-bor-vi-det/

I would appreciate help on this. Thanks.

Henrik Steen, Oslo, Norway

The page I need help with: [log in to see the link]