How to add thumbnail to blog homepage in supply template?

Hi all

I wondered if anyone can help - I can’t work out how to display thumbnails or images on the blog homepage in the supply template. Posts just show up as ugly subject headers and preview text, but nothing else - even though I’ve uploaded images in the posts themselves and via the edit area

I’ve read that the workaround is to add a block at the top of a post and insert an image - but that’s doing nothing

Any ideas or help would be really appreciated as it’s the inky downside I’ve found to this template so far but it’s a big one for my site!!!

Thanks