Change number of posts in main index

Hello all,

I have (I think) a simple question. I am using the theme Jillij, which has been only slightly modified.

The main index.php page includes the most recent 9 posts. Since I have a lot of photos, this takes a long time to load.

I want to change to the 3 most recent posts, and in the future, possible to only the 1 most recent post.

It seems I should be able to do this easily in the theme editor, but I can’t figure it out.

Thanks!