What file to tweak to move main blog image (main entry view) ?

I'm trying to move the main blog image up to go just under the title and before the 'posted by' info (see screenshot)

I use POLISH theme and I thought the file to tweak would be the blog.item file in that themes folder... in that file I see the page structure and moved the main blog code higher up - but it doesn't seem to make any difference.... Did I get the wrong file to tweak?

Thanks