How to make sure that each post shows up in respective post grid (under the Page where it belongs)?

Hi,

When I bought the Post Grid plugin, I thought it would look great sorting my posts under each Page, according to category. However, my posts end up mixing their categories in the Pages where I add the Post Grid shortlink.

Obiously, I'm doing something wrong! If you look at my site, in the menu you'll see, under 'Books & Reading' that I have the two sub-Pages 'Book Reviews' and 'Poem of the Day'. My idea was to have all the posts (only have a few, the site is new!) within the category 'Book Reviews' under that Page and those categorised as 'Poem of the Day' under its own, but they all end up together?

I have watched your video, but can't see how to fix it, not in the post settings nor the Post Grid settings.

Thank you in advance for your help, assistance and time.

Best wishes, Erika