How can I make my featured photo span the whole width of the blog

Try adding this to your custom CSS:

.single-post .entry-featured img {
  width: 100%;
}

Hi @domenica1
you can try this

.entry-featured img{
width:100%;
}

but the best way would be to use the minimum recommended image size from the documentation https://www.cssigniter.com/docs/olsen-light/

Glad I could help @domenica1

I’d like to ask you, if you like the theme and could take a minute to review it here it would help us a lot!