Setting entire page full justify???

Everything like that should be done in the stylesheet, not in the posts or Pages.

stylesheet? Can you possibly elaborate a little bit more?

Well, I could… but if you want to be the webmaster of your own blog you better start learning about HTML and CSS.
You don’t need any of the above if you just want to blog. In the moment you wish to change things in your blog’s layout, look etc. – you need to learn the basics.
Start here: https://www.w3schools.com/css/default.asp

Also note that around here when we say “stylesheet” we are typically referring to the style.css of an installed theme.