Blog template- Minimal Change image size

I am using the minimal blog template. The round images are just SO SMALL!! Is there a way to edit the size of these?

I actually prefer the other blog templates but want square images on the main post area instead of rectangle, is this possible??

Thank you so much. I’m just getting back into editing my site, so please be kind. I’m not super up on all the lingo and coding.

Thank you!

Heidi