How to order featured posts by date so that latest posts are shown

Hello,

Hopefully someone can help as my content is getting stale.

So, twenty fourteen is set up to only show your first six posts with the featured tag (if you want a grid or a slider for your homepage).

The rest of your posts get bumped down the page, so that your latest post, even if it has the featured tag, appears underneath your nice grid or slider on your homepage. This means that inevitably, content goes stale.

What I need help with is to tweak the code in the theme so that when I create a new post, and assign the featured tag to it, it appears in the featured content section of my homepage grid.

Does anyone know the code to add a php query to make this happen?
I am using a child theme, so from what I understand, I probably just need to add a separate functions file for this. I just don’t know php code.

Website example: https://www.newjewishconvert.co.uk

Help much appreciated,

Thank you for reading,

Jessica