Adding more posts on grid page

hi there, great theme! really smooth and simple.
but i’m trying to have more than 9 posts appear on the first grid page and can’t seem to figure out how. any advice on what to edit (or maybe there’s a simple setting i missed).

i’m also not opposed to no ‘older posts’ and just have everything appear on one page (if that’s easier to implement).

any help would be great.
cheers!