Journal creation — a marriage of Canva & CreateSpace templates for Word

What does it take to create your own journal (or planner or workbook) using Canva? And what is the best or the easiest way to go about designing its interior pages? What if you start with a Word document? What do you need to know in order to make sure it will look as good in a printed book as it does on your screen — or better? I spent several days designing the interior of my journal on Canva....