How to customize/edit shopify theme PAGES?

Hello,

I am no developer or anything, I just use shopify here and there.
I recently uploaded a Premium theme to my store, I can customize the homepage as usual with the shopify customizer, but I want to also customize and edit the other pages that comes with the website, the template suffixes per say. Im looking to be led into the right direction. Any help is appreciated;

Thank you.