You create a widget (<div class='sk-ww-rss-feed' data-embed-id='25357724'></div><script src='https://widgets.sociablekit.com/rss-feed/widget.js' async defer></script>) and copy it a block using raw.

To make it simple. You paste the RSS feed into  https://www.sociablekit.com/  and on this site it will create a widget that you can easily copy the code into block(raw). That simple.